Showing papers on "Mode volume published in 2019"

Probing 10 μK stability and residual drifts in the cross-polarized dual-mode stabilization of single-crystal ultrahigh- Q optical resonators

Abstract: The thermal stability of monolithic optical microresonators is essential for many mesoscopic photonic applications such as ultrastable laser oscillators, photonic microwave clocks, and precision navigation and sensing. Their fundamental performance is largely bounded by thermal instability. Sensitive thermal monitoring can be achieved by utilizing cross-polarized dual-mode beat frequency metrology, determined by the polarization-dependent thermorefractivity of a single-crystal microresonator, wherein the heterodyne radio-frequency beat pins down the optical mode volume temperature for precision stabilization. Here, we investigate the correlation between the dual-mode beat frequency and the resonator temperature with time and the associated spectral noise of the dual-mode beat frequency in a single-crystal ultrahigh-Q MgF2 resonator to illustrate that dual-mode frequency metrology can potentially be utilized for resonator temperature stabilization reaching the fundamental thermal noise limit in a realistic system. We show a resonator long-term temperature stability of 8.53 μK after stabilization and unveil various sources that hinder the stability from reaching sub-μK in the current system, an important step towards compact precision navigation, sensing, and frequency reference architectures. Researchers in California have improved the thermal stability of tiny optical microresonators for use in high-precision timing and global navigation technologies. Ultrahigh-quality whispering gallery optical microresonators work by guiding the light from two differently-polarized lasers around the resonator circumference, which is carefully designed to have particular resonant frequencies. However, microresonators are extremely sensitive to temperature changes, and the impact of laser-induced heating, heat diffusion, and thermal expansion over time is detrimental to performance. Jinkang Lim and Chee Wei Wong at the University of California, US, and co-workers have shown that, by locking the dual-mode beat frequency of the lasers to a radio-frequency clock, the resulting suppression of thermal noise and frequency drift can enhance the long-term thermal stability of optical microresonators. This novel solution could result in microresonators stable enough to be used in space.

Probing 10 {\mu}K stability and residual drifts in the cross-polarized dual-mode stabilization of single-crystal ultrahigh-Q optical resonators

Abstract: The thermal stability of monolithic optical microresonators is essential for many mesoscopic photonic applications such as ultrastable laser oscillators, photonic microwave clocks, and precision navigation and sensing. Their fundamental performance is largely bounded by thermal instability. Sensitive thermal monitoring can be achieved by utilizing cross-polarized dual-mode beat frequency metrology, determined by the polarization-dependent thermorefractivity of a single-crystal microresonator, wherein the heterodyne radio-frequency beat pins down the optical mode volume temperature for precision stabilization. Here, we investigate the correlation between the dual-mode beat frequency and the resonator temperature with time and the associated spectral noise of the dual-mode beat frequency in a single-crystal ultrahigh-Q MgF2 resonator to illustrate that dual-mode frequency metrology can potentially be utilized for resonator temperature stabilization reaching the fundamental thermal noise limit in a realistic system. We show a resonator long-term temperature stability of 8.53 {\mu}K after stabilization and unveil various sources that hinder the stability from reaching sub-{\mu}K in the current system, an important step towards compact precision navigation, sensing and frequency reference architectures.

Tip-enhanced strong coupling spectroscopy, imaging, and control of a single quantum emitter.

Abstract: Optical cavities can enhance and control light-matter interactions. This level of control has recently been extended to the nanoscale with single emitter strong coupling even at room temperature using plasmonic nanostructures. However, emitters in static geometries, limit the ability to tune the coupling strength or to couple different emitters to the same cavity. Here, we present tip-enhanced strong coupling (TESC) with a nanocavity formed between a scanning plasmonic antenna tip and the substrate. By reversibly and dynamically addressing single quantum dots, we observe mode splitting up to 160 meV and anticrossing over a detuning range of ~100 meV, and with subnanometer precision over the deep subdiffraction-limited mode volume. Thus, TESC enables previously inaccessible control over emitter-nanocavity coupling and mode volume based on near-field microscopy. This opens pathways to induce, probe, and control single-emitter plasmon hybrid quantum states for applications from optoelectronics to quantum information science at room temperature.

Space-compatible cavity-enhanced single-photon generation with hexagonal boron nitride

Abstract: Sources of pure and indistinguishable single-photons are critical for near-future optical quantum technologies. Recently, color centers hosted by two-dimensional hexagonal boron nitride (hBN) have emerged as a promising platform for high luminosity room temperature single-photon sources. Despite the brightness of the emitters, the spectrum is rather broad and the single-photon purity is not sufficient for practical quantum information processing. Here, we report integration of such a quantum emitter hosted by hBN into a tunable optical microcavity. A small mode volume of the order of $\lambda^3$ allows us to Purcell enhance the fluorescence, with the observed excited state lifetime shortening. The cavity significantly narrows the spectrum and improves the single-photon purity by suppression of off-resonant noise. We explore practical applications by evaluating the performance of our single-photon source for quantum key distribution and quantum computing. The complete device is compact and implemented on a picoclass satellite platform, enabling future low-cost satellite-based long-distance quantum networks.

Ultrasmall Mode Volume Hyperbolic Nanocavities for Enhanced Light–Matter Interaction at the Nanoscale

Abstract: Cavities are the building blocks for multiple photonic applications from linear to nonlinear optics and from classical optics to quantum electrodynamics. Hyperbolic metamaterial cavities are one cl...

Low-impedance superconducting microwave resonators for strong coupling to small magnetic mode volumes

Abstract: Recent experiments on strongly coupled microwave and ferromagnetic resonance modes have focused on large volume bulk crystals such as yttrium iron garnet, typically of millimeter-scale dimensions. We extend these experiments to lower volumes of magnetic material by exploiting low-impedance lumped-element microwave resonators. The low impedance equates to a smaller magnetic mode volume, which allows us to couple to a smaller number of spins in the ferromagnet. Compared to previous experiments, we reduce the number of participating spins by two orders of magnitude, while maintaining the strength of the coupling rate. Strongly coupled devices with small volumes of magnetic material may allow the use of spin orbit torques, which require high current densities incompatible with existing structures.

High-Q, low-mode-volume microsphere-integrated Fabry–Perot cavity for optofluidic lasing applications

Abstract: We develop a hybrid optofluidic microcavity by placing a microsphere with a diameter ranging from 1 to 4 μm in liquid-filled plano-plano Fabry–Perot (FP) cavities, which can provide an extremely low effective mode volume down to 0.3–5.1 μm3 while maintaining a high Q-factor up to 1×104–5×104 and a finesse of ∼2000. Compared to the pure plano-plano FP cavities that are known to suffer from the lack of mode confinement, diffraction, and geometrical walk-off losses as well as being highly susceptible to mirror misalignment, our microsphere-integrated FP (MIFP) cavities show strong optical confinement in the lateral direction with a tight mode radius of only 0.4–0.9 μm and high tolerance to mirror misalignment as large as 2°. With the microsphere serving as a waveguide, the MIFP is advantageous over a fiber-sandwiched FP cavity due to the open-cavity design for analytes/liquids to interact strongly with the resonant mode, the ease of assembly, and the possibility to replace the microsphere. In this work, the main characteristics of the MIFP, including Q-factor, finesse, effective mode radius and volume, and their dependence on the surrounding medium’s refractive index, mirror spacing, microsphere position inside the FP cavity, and mirror misalignment, are systematically investigated using a finite-element method. Then, by inserting dye-doped polystyrene microspheres of various sizes into the FP cavity filled with water, we experimentally realize single-mode MIFP optofluidic lasers that have a lasing threshold as low as a few microjoules per square millimeter and a lasing spot radius of only ∼0.5 μm. Our results suggest that the MIFP cavities provide a promising technology platform for novel photonic devices and biological/chemical detection with ultra-small detection volumes.

Record Purcell factors in ultracompact hybrid plasmonic ring resonators.

Abstract: For integrated optical devices and traveling-wave resonators, realistic use of the superior wave-matter interaction offered by plasmonics is impeded by ohmic loss, which increases rapidly with mode volume reduction. In this work, we report composite hybrid plasmonic waveguides (CHPWs) that are not only capable of guiding subwavelength optical mode with long-range propagation but also unrestricted by stringent requirements in structural, material, or modal symmetry. In these asymmetric CHPWs, the versatility afforded by coupling dissimilar plasmonic modes provides improved fabrication tolerance and more degrees of device design optimization. Experimental realization of CHPWs demonstrates propagation loss and mode area of 0.03 dB/μm and 0.002 μm2, corresponding to the smallest combination among long-range plasmonic structures reported to date. CHPW ring resonators with 2.5-μm radius were realized with record Purcell factor compared with existing plasmonic and dielectric resonators of similar radii.

Nonlinear characterization of silica and chalcogenide microresonators

Abstract: Microresonators offer an attractive combination of high quality factors and small optical mode volume. They have emerged as a unique platform for the study of fundamental physics and for applications ranging from exquisite sensors to miniature optical combs. Characterizing the linear and nonlinear properties of a microresonator is the first step toward new applications. Here, we present a novel in situ method to measure the nonlinear refractive index and absorption coefficient in microresonators. Laser-scanned transmission spectra are fitted by a comprehensive theoretical model that includes the thermo-optic effect, Kerr effect, and back-coupling of counter-propagating modes. The effectiveness of our technique is demonstrated by evaluating the nonlinear indices and optical absorption of silica and chalcogenide (As2S3) microspheres at 1.55 μm. Significantly, our method also quantifies important parameters including the quality factor, thermal relaxation time, and back-coupling coefficient at the same time. Our findings provide a powerful new approach for characterization of microresonators and optical materials and pave the way for new opportunities in the area.

Microcavity-Mediated Spectrally Tunable Amplification of Absorption in Plasmonic Nanoantennas.

Abstract: Nanoantenna–microcavity hybrid systems offer unique platforms for the study and manipulation of light at the nanoscale, since their constituents have either low mode volume or long photon storage time. A nearby dielectric optical cavity can modify the photonic environment surrounding a plasmonic nanoantenna, presenting opportunities to sculpt its spectral response. However, matching the polar opposites for enhanced light–matter interactions remains challenging, as the antenna can be rendered transparent by the cavity through destructive Fano interferences. In this work, we tackle this issue by offering a new plasmonic–photonic interaction framework. By coupling to a photonic crystal guided resonance, a gold nanostar delivers 1 order of magnitude amplified absorption, and the ultrasharp Lorentzian-line-shaped hybrid resonance is continuously tunable over a broad spectral range by scanning of the incidence angle. Our intuitive coupled mode model reveals that a distinct optical pathway highlighting the cavit...

Exciton-Plasmon Energy Exchange Drives the Transition to a Strong Coupling Regime.

Abstract: We present a model for exciton-plasmon coupling based on an energy exchange mechanism between quantum emitters (QE) and localized surface plasmons in metal-dielectric structures. Plasmonic correlations between QEs give rise to a collective state exchanging its energy cooperatively with a resonant plasmon mode. By defining carefully the plasmon mode volume for a QE ensemble, we obtain a relation between QE-plasmon coupling and a cooperative energy transfer rate that is expressed in terms of local fields. For a single QE near a sharp metal tip, we find analytically the enhancement factor for QE-plasmon coupling relative to QE coupling to a cavity mode. For QEs distributed in an extended region enclosing a plasmonic structure, we find that the ensemble QE-plasmon coupling saturates to a universal value independent of system size and shape, consistent with the experiment.

Ultra-low mode volume on-substrate silicon nanobeam cavity

Abstract: We design and fabricate an on-substrate bowtie photonic crystal (PhC) cavity in silicon. By optimizing the bowtie shapes in the unit cells of the PhC cavity, the maximum of the electric field can be highly confined in the bowtie tips. Due to such confinement, an ultra-low mode volume of ∼0.1(λ/nSi)3 is achieved, which is more than an order of magnitude smaller than the previous on-substrate nanobeam cavities. An ultra-high quality (Q) factor as large as 106 is predicted by simulation, and up to 1.4×104 is measured in experiment. The observation of pronounced thermo-optic bistability is consistent with the strong confinement of light in the cavities.

Fabrication of a nanofiber Bragg cavity with high quality factor using a focused helium ion beam.

Abstract: Nanofiber Bragg cavities (NFBCs) are solid-state microcavities fabricated in an optical tapered fiber. NFBCs are promising candidates as a platform for photonic quantum information devices due to their small mode volume, ultra-high coupling efficiencies, and ultra-wide tunability. However, the quality (Q) factor has been limited to be approximately 250, which may be due to limitations in the fabrication process. Here we report high Q NFBCs fabricated using a focused helium ion beam. Whenan NFBC with grooves of 640 periods is fabricated, the Q factor is over 4170, which is more than 16 times larger than that previously fabricated using a focused gallium ion beam.

A tunable High-Q millimeter wave cavity for hybrid circuit and cavity QED experiments

Abstract: The millimeter wave (mm-wave) frequency band provides exciting prospects for quantum science and devices, since many high-fidelity quantum emitters, including Rydberg atoms, molecules and silicon vacancies, exhibit resonances near 100 GHz. High-Q resonators at these frequencies would give access to strong interactions between emitters and single photons, leading to rich and unexplored quantum phenomena at temperatures above 1K. We report a 3D mm-wave cavity with a measured single-photon internal quality factor of $3 \times 10^{7}$ and mode volume of $0.14 \times \lambda^3$ at $98.2$ GHz, sufficient to reach strong coupling in a Rydberg cavity QED system. An in-situ piezo tunability of $18$ MHz facilitates coupling to specific atomic transitions. Our unique, seamless and optically accessible resonator design is enabled by the realization that intersections of 3D waveguides support tightly confined bound states below the waveguide cutoff frequency. Harnessing the features of our cavity design, we realize a hybrid mm-wave and optical cavity, designed for interconversion and entanglement of mm-wave and optical photons using Rydberg atoms.

Control of Whispering Gallery Modes and PT-Symmetry Breaking in Colloidal Quantum Dot Microdisk Lasers with Engineered Notches

Abstract: Whispering gallery mode resonators have been demonstrated to be a great way to achieve superior optical cavities with high quality factor and small mode volume. However, due to the high sensitivity of these modes to the properties of the resonator boundary, they are susceptible to parasitic splitting of clockwise and counterclockwise modes. In this work, we investigate the effect of implantation of an engineered notch into the boundary of a circular microdisk resonator fabricated from colloidal quantum dots, which are particularly sensitive to boundary defects. We observed a strong reduction of parasitic mode splitting with introduction of a large engineered notch, as well as enhanced directionality of laser emission. We further investigate the performance of these resonators in evanescently coupled pairs, where the modal interaction allows modulation of laser behavior through variation of the gain and loss induced by the optical pump. We show that two distinct cases of modal interaction can be achieved by adjusting the size of the engineered notch, providing a bridge between intra- and interdisk modal interactions for laser spectral control.

Mode conversion and orbital angular momentum transfer among multiple modes by helical gratings

Abstract: The coupling feature of helical gratings (HGs) has been studied on flexible conversion between two orbital angular momentum (OAM) modes by both the transverse and longitudinal modulation of HGs. Apart from one to one OAM exchange, HGs can achieve OAM transfer among multiple modes, provided both the helix and phase matching conditions are well satisfied for successive coupling. It is contributed from the fold number of modulation fringes of HGs and the difference multiplication of propagation constants between two of the successive modes. Based on the coupled mode theory, we investigate the mode conversion and OAM transfer among three modes using a 3 fold HGs in a ring core fiber, and numerically simulate it by transmission matrix. Our work about the multiple modes transferring can be regarded as an extension of mode coupling for optical gratings, and might flourish the mode conversion, as well as OAM manipulation in optics fields.

Cavity QED Based on Thermal Atoms Interacting with a Photonic Crystal Cavity: A Feasibility Study

Abstract: The paradigm of cavity QED is a two-level emitter interacting with a high quality factor single mode optical resonator. The hybridization of the emitter and photon wave functions mandates large vacuum Rabi frequencies and long coherence times; features that so far have been successfully realized with trapped cold atoms and ions and localized solid state quantum emitters such as superconducting circuits, quantum dots, and color centers. Thermal atoms on the other hand, provide us with a dense emitter ensemble and in comparison to the cold systems are more compatible with integration, hence enabling large-scale quantum systems. However, their thermal motion and large transit time broadening is a major challenge that has to be circumvented. A promising remedy could benefit from the highly controllable and tunable electromagnetic fields of a nano-photonic cavity with strong local electric-field enhancements. Utilizing this feature, here we calculate the interaction between fast moving, thermal atoms and a nano-beam photonic crystal cavity (PCC) with large quality factor and small mode volume. Through fully quantum mechanical calculations, including Casimir-Polder potential (i.e. the effect of the surface on radiation properties of an atom) we show, when designed properly, the achievable coupling between the flying atom and the cavity photon would be strong enough to lead to Rabi flopping in spite of short interaction times. In addition, the time-resolved detection of different trajectories can be used to identify single and multiple atom counts. This probabilistic approach will find applications in cavity QED studies in dense atomic media and paves the way towards realizing coherent quantum control schemes in large-scale macroscopic systems aimed at out of the lab quantum devices.

Spectral and Spatial Characteristics of the Electromagnetic Modes in a Tunable Optical Microcavity Cell for Studying Hybrid Light–Matter States

Abstract: Studies of resonance interaction between matter and localized electromagnetic field in a cavity have recently attracted much interest because they offer the possibility of controllably modifying some of the fundamental material properties. However, despite the large number of such studies, these is no universal approach that would allow investigation of sets of different samples with wide variation of the main experimental parameters of the optical modes. In this work, the main optical parameters of a previously developed universal tunable microcavity cell, i.e., the Q factor and mode volume, as well as their dependence on the characteristics of cavity mirrors and spacing between them, are analyzed. The results obtained will significantly expand the scope of applications of resonance interaction between light and matter, including such effects as the enhancement of Raman scattering, long-range resonance nonradiative energy transfer, and modification of chemical reaction rates.

Droplet Raman laser coupled to a standard fiber

Abstract: We fabricate a tapered fiber coupler, position it near an ultrahigh-Q resonator made from a microdroplet, and experimentally measure stimulated Raman emission. We then calculate the molecular vibrational mode associated with each of the Raman lines and present it in a movie. Our Raman laser lines show themselves at a threshold of 160 μW input power, the cold-cavity quality factor is 250 million, and mode volume is 23 μm3. Both pump and Raman laser modes overlap with the liquid phase instead of just residually extending to the fluid.

Tunable strong plasmon-exciton coupling between single silver nanocube dimer and J-aggregates

Abstract: In this paper, single silver nanocube dimer with nanometer-sized gap is designed and numerically simulated. We demonstrate that the electric fields can be highly confined in the gap of nanocube dimer, leading to ultrasmall mode volume of ≈2 × 10-7 μm3. Furthermore, the strong plasmon-exciton coupling in single nanocube dimer coupled with J-aggregate molecules is investigated using coupled oscillator model and we show that the strong plasmon-exciton coupling can be tuned by changing the background refractive index and the concentration of J-aggregate molecules. The tuning of dual strong plasmon-exciton couplings between single rounded silver nanocube dimer and J-aggregate molecules is also investigated, and dual strong couplings can be achieved closely approaching the quantum optics limit benefiting from the ultrasmall mode volume of the proposed system. The proposed systems can be easily prepared and have high experimental feasibility, which has potential applications in integrated nanophotonics such as sensing and all-optical switches.

Photonic-Plasmonic Hybrid 2D-Pillar Cavity for Mode Confinement With Subwavelength Volume

Abstract: We present a two-dimensional photonic-plasmonic hybrid cavity design by exploring the photonic bandgap properties and the plasmonic characteristics. The FDTD simulation tool was used to optimize the cavity parameters. The design was achieved by introducing a layer of defect rods in the 2D-PhC pillar structure on a thin metal slab supported by a glass substrate. The excited defect mode is confined in the photonic-plasmonic bandgap, it is spatially restricted on the symmetry plane and the plasmonic characteristics offer enhanced confinement in the vertical plane close to the metal layer. The optimized size of the defect rods as well as the thickness of the metal layer can offer an enhanced Q factor of 850, and subwavelength mode volume of 0.07 ( $\lambda $ /n)3 with a maximum intensity distribution is concentrated in the defect rods.

Interference-modulated photon statistics in whispering-gallery-mode microresonator optomechanics

Abstract: Whispering-gallery-mode (WGM) microresonator optomechanical systems that can attain high quality factors, exhibit small optical mode volume, and can be excited through their evanescent field are versatile platforms for both theoretical and experimental studies in quantum and nonlinear optics. Investigating photon statistical properties in WGM microresonator optomechanical systems is an important avenue to understand their inner interaction mechanism. Here, the interference-modulated photon statistics in a three-mode coupling, i.e., a pair of counterpropagating optical cavity modes and a mechanical mode, in WGM microresonator optomechanical systems is studied. In the case that one optical mode is driven by an external field, strong antibunching photon statistics can be observed in the presence of mode coupling. When the two cavity modes are driven simultaneously, it is found that the photon statistical properties can be well steered by modulating the interference between different transition paths with the help of the amplitudes of the two input fields and their relative phase. Especially, we show in detail that the antibunching photon statistics can be optimized within the weak optomechanical coupling regime by properly adjusting the relative phase. We also find that it is necessary to prepare the mechanical resonator near to the ground state to eliminate the detrimental effect of thermal phonon number on the photon statistical properties. This investigation can deepen our understanding of the interaction between clockwise or counterclockwise light and mechanical motion as well as be useful for the construction of integrated on-chip single-photon sources.

Continuously-tunable light-matter coupling in optical microcavities with 2D semiconductors

Abstract: A theoretical variation between the two distinct light-matter coupling regimes, namely weak and strong coupling, becomes uniquely feasible in open optical Fabry-Perot microcavities with low mode volume, as discussed here. In combination with monolayers of transition-metal dichalcogenides (TMDCs) such as WS2, which exhibits a large exciton oscillator strength and binding energy, the room-temperature observation of hybrid bosonic quasiparticles, referred to as exciton-polaritons and characterized by a Rabi splitting, comes into reach. In this context, our simulations using the transfer-matrix method show how to tailor and alter the coupling strength actively by varying the relative field strength at the excitons' position - exploiting a tunable cavity length, a transparent PMMA spacer layer and angle-dependencies of optical resonances. Continuously tunable coupling for future experiments is hereby proposed, capable of real-time adjustable Rabi splitting as well as switching between the two coupling regimes. Being nearly independent of the chosen material, the suggested structure could also be used in the context of light-matter-coupling experiments with quantum dots, molecules or quantum wells. While the adjustable polariton energy levels could be utilized for polariton-chemistry or optical sensing, cavities that allow working at the exceptional point promise the exploration of topological properties of that point.

Reduced Symmetric 2D Photonic Crystal Cavity with Wavelength Tunability

Abstract: In this paper, we propose a microcavity supported by a designed photonic crystal structure (PhC) that supplies both tunability of cavity modes and quality factor of cavity. Low symmetric defect region provides a trigger effect for the frequency shifting by means of rotational manipulation of small symmetry elements. Deviation of effective filling ratio as a result of rotational modification within the defect region results in the emanation of cavity modes at different frequencies. Here, we numerically demonstrate the frequency shifting for each obtained mode with respect to defect region architecture. In addition to wavelength tunability, quality factor, mode volume, and Purcell factors are analyzed for the slightly modified structures. Also, electric field distributions of each mode that emerge at distinct frequencies have been also studied at adjusted frequency modes which are observed for all rotational modification scenarios as $\theta_{rot} =[0^\circ,15^\circ,30^\circ, 40^\circ] $. After the investigations in 2D of silicon material ($\epsilon_r=12$), 3D simulations are performed and the collected data is used for the stacking approximation of 3D structures to get the 2D, thus the cross-checking of the quality factor that acquired from the 2D simulation can be executed by comparison with 3D. Limited 3D results are projected to approximate 2D ones step by step and get an exponential trend which reaches in the limit to the $10^8$ value for Q-factor. Besides, 2D and 3D simulations of alumina ($\epsilon_r=9.61$) in terms of mode analysis and quality factor have been repeated considering the microwave experiments. Therefore, experimental analysis is compared with the numerical results and good agreement between the two is found.

Multi-wavelength large mode volume laser

Abstract: The invention relates to a multi-wavelength large mode volume laser, which uses a broadband laser gain medium and a chromatic dispersion optical element in a resonant cavity; the path separation of different resonant wavelengths on the laser gain medium is realized; the multi-wavelength large mode volume laser common path output is further realized. The multi-wavelength large mode volume laser comprises a pumping source, a resonant cavity full reflection mirror, a resonant cavity output coupling mirror, the laser grain medium and the chromatic dispersion optical element, wherein the chromaticdispersion optical element realizes different paths of different resonant wavelengths on the laser gain medium; the wide-gain laser grain medium realizes multi-wavelength laser gain; the mode competition among different laser wavelengths is avoided; the simultaneous resonance of multi-wavelength laser is realized. The invention provides a novel laser structure; the laser power density of the lasergain medium can be reduced; the heat radiation area is increased; the laser output power is improved; the multi-wavelength laser common path high beam quality output is realized.

Common mode noise suppression of optical frequency combs for optical clock applications

Abstract: The disclosure relates in some aspects to a two-point locking system for stabilizing a frequency comb oscillator using at least two optical transitions of the same atomic/molecular sample. In an example, an optical reference sample is provided that is characterized by two or more optical transitions. A coherent light source provides polychromatic coherent light (such as an optical frequency comb). The beams of light, occupying the same spatial mode volume or separated in space, and having frequencies in the vicinity of the optical transitions of the reference sample, interrogate the resonances of the reference sample. Interrogation signals obtained using phase/frequency/amplitude spectroscopy or other spectroscopy techniques are then used to stabilize the frequency harmonics of the light. If the harmonics belong to the same coherent frequency comb, the entire comb becomes stabilized using this procedure. In an illustrative example, a stable atomic optical clock is provided using these techniques.

Ultra-high Purcell factor using long-range modes in asymmetric plasmonic waveguides.

Abstract: For integrated optical devices, realistic utilization of the superior wave-matter interaction offered by plasmonics is typically impeded by optical losses, which increase rapidly with mode volume reduction. Although coupled-mode plasmonic structures has demonstrated effective alleviation of the loss-confinement trade-off, stringent symmetry requirements must be enforced for such reduction to prevail. In this work, we report an asymmetric plasmonic waveguide that is not only capable of guiding subwavelength optical mode with long-range propagation, but is also unrestricted by structural, material, or modal symmetry. In these composite hybrid plasmonic waveguides (CHPWs), the versatility afforded by coupling dissimilar plasmonic structures, within the same waveguide, allow better fabrication tolerance and provide more degrees of design freedom to simultaneously optimize various device attributes. The CHPWs used to demonstrated the concept in this work, exhibit propagation loss and mode area of only 0.03 dB/{\mu}m and 0.002 {\mu}m^2 respectively, corresponding to the smallest combination amongst experimentally demonstrated long-range plasmonic structures to-date. Moreover, CHPW micro-rings were realized with record in/out coupling excitation efficiency (71%), extinction ratio (29 dB), as well as Purcell factor (1.5\times10^4).

Increasing the Fundamental Mode Volume in Nd:YAG Laser and Stabilizing Against Mechanical and Thermal Disturbance in High Power Pumping Regime

Abstract: The subject of this research is to investigating the advantages of a special stable resonator relative to the flat-symetric stable resonator scheme in high power pumped Nd:YAG lasers. At first a discussion about some convetional resonators used in high power Nd:YAG lasers is presented considering the advantages and shortcomes of each resonator scheme. Then by using distributed refractive power model(DRP), for a typical high power side pumped Nd:YAG laser ,and investigating the stability regions, a non symmetric resonator scheme is proposed which gives single transverse mode and demonstrates higher fundamental mode volume (12 times greater) compared with flat-symetric scheme. Also misalignment sensivity of the presented resonator has been studied and compared with flat-symetric resonator, using numerical calculation and simulation with GLAD software. The results of this research revealed that in high level of pumped power, it is also possible to achieve high fundamental mode volume and make the resonator stable due to thermal and mechanical disturbance.