Showing papers on "Injection locking published in 2017"

Conditions for reservoir computing performance using semiconductor lasers with delayed optical feedback.

Abstract: Photonic implementations of reservoir computing (RC) have been receiving considerable attention due to their excellent performance, hardware, and energy efficiency as well as their speed. Here, we study a particularly attractive all-optical system using optical information injection into a semiconductor laser with delayed feedback. We connect its injection locking, consistency, and memory properties to the RC performance in a non-linear prediction task. We find that for partial injection locking we achieve a good combination of consistency and memory. Therefore, we are able to provide a physical basis identifying operational parameters suitable for prediction.

Parametric Oscillation, Frequency Mixing, and Injection Locking of Strongly Coupled Nanomechanical Resonator Modes.

Abstract: We study locking phenomena of two strongly coupled, high quality factor nanomechanical resonator modes to a common parametric drive at a single drive frequency in different parametric driving regimes. By controlled dielectric gradient forces we tune the resonance frequencies of the flexural in-plane and out-of-plane oscillation of the high stress silicon nitride string through their mutual avoided crossing. For the case of the strong common parametric drive signal-idler generation via nondegenerate parametric two-mode oscillation is observed. Broadband frequency tuning of the very narrow linewidth signal and idler resonances is demonstrated. When the resonance frequencies of the signal and idler get closer to each other, partial injection locking, injection pulling, and complete injection locking to half of the drive frequency occurs depending on the pump strength. Furthermore, satellite resonances, symmetrically offset from the signal and idler by their beat note, are observed, which can be attributed to degenerate four-wave mixing in the highly nonlinear mechanical oscillations.

16 Gb/s PAM4 UWOC system based on 488-nm LD with light injection and optoelectronic feedback techniques

Abstract: A 16 Gb/s four-level pulse amplitude modulation (PAM4) underwater wireless optical communication (UWOC) system based on 488-nm laser diode (LD) with light injection and optoelectronic feedback techniques is proposed and successfully demonstrated. Experimental results show that such a 1.8-GHz 488-nm blue light LD with light injection and optoelectronic feedback techniques is enough forceful for a 16 Gb/s PAM4 signal underwater link. To the authors’ knowledge, this study is the first to successfully adopt a 488-nm LD transmitter with light injection and optoelectronic feedback techniques in a PAM4 UWOC system. By adopting a 488-nm LD transmitter with light injection and optoelectronic feedback techniques, good bit error rate performance (offline processed by Matlab) and clear eye diagrams (measured in real-time) are achieved over a 10-m underwater link. The proposed system has the potential to play a vital role in the future UWOC infrastructure by effectively providing high transmission rate (16 Gb/s) and long underwater transmission distance (10 m).

Modulation of Coherently Coupled Phased Photonic Crystal Vertical Cavity Laser Arrays

Abstract: The modulation properties of two-element photonic crystal ion-implanted coherently coupled vertical cavity surface emitting laser arrays emitting at 850 nm are reported. Single mode emission into either the in-phase or out-of-phase supermode and significant modulation bandwidth enhancement are obtained for both operating conditions. We model our device as a monolithically integrated, mutually optically injection-locked laser system and show that the phase detuning and injection ratio between array elements are critical parameters influencing modulation bandwidth. Comparison of our experimental measurements to our model is consistent with mutual injection locking. Modulation bandwidth greater than 30 GHz and up to 37 GHz is consistently found for several array designs. We show the modulation response can be tailored for different applications.

Injection locking of an electro-optomechanical device

Abstract: Advances in optomechanics have enabled significant achievements in precision sensing and control of matter, including detection of gravitational waves and cooling of mechanical systems to their quantum ground states. Recently, the inherent nonlinearity in the optomechanical interaction has been harnessed to explore synchronization effects, including the spontaneous locking of an oscillator to a reference injection signal delivered via the optical field. Here, we present, to the best of our knowledge, the first demonstration of a radiation-pressure-driven optomechanical system locking to an inertial drive, with actuation provided by an integrated electrical interface. We use the injection signal to suppress the drift in the optomechanical oscillation frequency, strongly reducing phase noise by over 55 dBc/Hz at 2 Hz offset. We further employ the injection tone to tune the oscillation frequency by more than 2 million times its narrowed linewidth. In addition, we uncover previously unreported synchronization dynamics, enabled by the independence of the inertial drive from the optical drive field. Finally, we show that our approach may enable control of the optomechanical gain competition between different mechanical modes of a single resonator. The electrical interface allows enhanced scalability for future applications involving arrays of injection-locked precision sensors.

High-Resolution Balanced Microwave Material Sensor With Extended Dielectric Range

Abstract: This paper proposes a new design method to achieve adverse-resistant microwave sensors using balanced structure of two sensors. Any kinds of sensors can be used in the presented balanced architecture. However, a new kind of high-resolution microwave material sensor, based on the injection locking phenomenon, is presented and used in this paper. By injecting a low-power level and low-phase noise signal to an oscillator, an injection-locked oscillator with a very small lock range is achieved with a very high sensitivity to its resonator condition. In the balanced structure, for a standard sample over one branch and an arbitrary sample over the other, the difference between center frequencies and lock ranges of oscillators can be measured at once. Therefore, the dielectric constant and loss tangent of unknown samples are calculated while the adverse environmental variations have the same effects on both branches and are compensated automatically without additional sensors and environmental controlling system. Moreover, it is indicated that using a simple frequency comparator with an output voltage instead of a spectrum analyzing system makes the system more practical and low cost. As an example for validation, a system is fabricated at 1 GHz and results of various states have been presented.

A 71–86-GHz Phased Array Transceiver Using Wideband Injection-Locked Oscillator Phase Shifters

Abstract: This paper presents the first phased array transceiver operating from 71 to 86 GHz using injection-locked oscillators (ILOs) for phase shifting. A folded-cascode ILO is proposed to extend the locking range of an array of oscillators. Frequency multiplication covers a 10-GHz tuning range with 23-dB power gain. Each ILO path covers more than ±300° and exhibits low amplitude variation with respect to phase shift range ( $3.4\times2.1$ mm2 area implementing in the 90-nm BiCMOS technology and consuming 386.4 mW in the TX mode and 286 mW in the RX mode per element.

A 2–11 GHz 7-Bit High-Linearity Phase Rotator Based on Wideband Injection-Locking Multi-Phase Generation for High-Speed Serial Links in 28-nm CMOS FDSOI

Abstract: Pushed by the ever-increasing demand of internet traffic, high-speed serial interfaces are expected to reach 400-Gb/s aggregate data rates in near future. At receiver (RX) side, phase rotators (PRs) are key blocks to align the phase of the local clock to the transitions of the incoming data and to sample the eye in the optimal position. Small phase step and high linearity are paramount in preserving the horizontal time margin, tightened by the reduced symbol duration at 25 Gb/s and beyond. Interpolation of $\pi $ /4-spaced signals is a viable means of improving linearity at high resolution, provided multi-phase signals with low phase error are available. An injection-locked ring oscillator (ILRO) with a mixed analog and digital calibration loop is proposed for high accuracy multi-phase generation over a wide frequency range and against large voltage and temperature variations. A phase detector (PD) based on two passive mixers measures the quadrature error and continuously tunes the oscillator to achieve low phase error. Concurrently, a window comparator monitors the PD output and drives digital coarse calibration in background. Two test chips have been fabricated in 28-nm CMOS fully depleted silicon on insulator technology. The stand-alone ILRO demonstrates 0.2–11.7 GHz frequency range with better than 1.5° quadrature phase error over ±20% supply and −40 °C to +120 °C temperature variations. Power consumption is scalable from 3 to 15 mW. When the ILRO drives the 7-bit PR, it demonstrates differential and integral non-linearity within 0.5 and 1.1 LSB, respectively, across the 2–11 GHz frequency range with 18.6-mW maximum power dissipation. Measured performances compare favorably against the state of the art and meet the requirements of >25 Gb/s multi-standard I/O RXs.

Millimeter-resolution long-range OFDR using ultra-linearly 100 GHz-swept optical source realized by injection-locking technique and cascaded FWM process

Abstract: In this paper, we propose and demonstrate a millimeter-resolution long-range optical frequency domain reflectometry (OFDR) using an ultra-linearly 100-GHz swept optical source realized by injection-locking technique and cascaded four-wave-mixing (FWM) process. The ultra-linear sweep is realized using an external modulation method with a linearly swept radio frequency (RF) signal. The RF signal sweeps from 16 GHz to 19.3 GHz, and the slave laser is injection-locked to the 8th-order sideband of the master laser, achieving a frequency sweeping span of ~25 GHz. By using the injection-locked frequency-swept laser as the optical source of OFDR, we obtain a spatial resolution of 4.2 mm over 10-km measurement range. A polarization beat length of 10.5 cm is measured benefiting from the high spatial resolution. To improve the spatial resolution further, FWM process is used to broaden the frequency sweeping span. Frequency sweeping span of ~100 GHz is achieved with cascaded FWM. We demonstrate a 1.1-mm spatial resolution over 2-km measurement range with the proposed ultra-linearly swept optical source.

Numerical study of ultrashort-optical-feedback-enhanced photonic microwave generation using optically injected semiconductor lasers at period-one nonlinear dynamics

Abstract: This study numerically investigates the enhancement of photonic microwave generation using an optically injected semiconductor laser operating at period-one (P1) nonlinear dynamics through ultrashort optical feedback. For the purpose of practical applications where system miniaturization is generally preferred, a feedback delay time that is one to two orders of magnitude shorter than the relaxation resonance period of a typical laser is emphasized. Various dynamical states that are more complicated than the P1 dynamics can be excited under a number of ultrashort optical feedback conditions. Within the range of the P1 dynamics, on one hand, the frequency of the P1 microwave oscillation can be greatly enhanced by up to more than three folds. Generally speaking, the microwave frequency enhances with the optical feedback power and phase, while it varies saw-wise with the optical feedback delay time. On the other hand, the purity of the P1 microwave oscillation can be highly improved by up to more than three orders of magnitude. In general, the microwave purity improves with the optical feedback power and delay time, while it only varies within an order of magnitude with the optical feedback phase. These results suggest that the ultrashort optical feedback provides the optically injected laser system with an extra degree of freedom to manipulate/improve the characteristics of the P1 microwave oscillation without changing the optical injection condition.

Miniaturized calcium beam optical frequency standard using fully-sealed vacuum tube with 10-15 instability.

Abstract: We implement a miniaturized calcium beam optical frequency standard using specially-designed fully-sealed vacuum tube, and realize the comparison with another calcium beam optical clock whose vacuum tube is sealed by flanges. The electron shelving detection method is adopted to improve the signal-to-noise ratio of the clock transition spectroscopy, and the readout laser is locked by modulation-free frequency locking technology based on Doppler effect. Injection locking is carried out to boost the power of the 657 nm master clock transition laser, thus ensuring the comparison. The fractional instability of the miniaturized calcium beam optical frequency standard using fully-sealed vacuum tube is 1.8×10-15 after 1600 s of averaging. Total volume of the system except for electronics is about 0.3 m3. To our knowledge, it's the first time to realize the optical frequency standard using fully-sealed vacuum tube. This work will promote the miniaturization and transportability of the optical clock based on atomic beam.

Injection locking of a terahertz quantum cascade laser to a telecommunications wavelength frequency comb

Abstract: High-resolution spectroscopy not only can identify atoms and molecules but also can provide detailed information on their chemical and physical environment and relative motion. In the terahertz frequency region of the electromagnetic spectrum, where many molecules have fundamental vibrational modes, there is a lack of powerful sources with narrow linewidths that can be used for absorption measurements or as local oscillators in heterodyne detectors. The most promising solid-state source is the THz frequency quantum cascade laser (QCL), however, the linewidth of this compact semiconductor laser is typically too broad for many applications, and its frequency is not directly referenced to primary frequency standards. In this work, we injection lock a QCL operating at 2 THz to a compact fiber-based telecommunications wavelength frequency comb, where the comb line spacing is referenced to a microwave frequency reference. This results in the QCL frequency locking to an integer harmonic of the microwave reference, and the QCL linewidth reducing to the multiplied linewidth of the microwave reference, <100 Hz. Furthermore, we perform phase-resolved detection of the locked QCL and measure the phase noise of the locked system to be −75 dBc/Hz at 10 kHz offset from the 2 THz carrier.

A 312-GHz CMOS Injection-Locked Radiator With Chip-and-Package Distributed Antenna

Abstract: This paper presents an injected-locked THz radiator integrating a half-quadrature voltage-controlled oscillator (HQVCO), four injection-locked frequency quadruplers (ILFQs), and a chip-and-package distributed antenna (DA). At the system level, an architecture based on injection locking is employed to allow individual optimization of the output power and the phase noise. At the circuit level, intrinsic-delay compensation and harmonic boosting techniques are proposed to optimize the phase noise of the HQVCO and the output power of the ILFQs, respectively. The proposed DA composed of four exciting elements on silicon chip and a primary radiator in low-temperature co-fired ceramic (LTCC) package features a wide bandwidth of 13% and a gain of 3.8 dBi without using lens at 312 GHz. Implemented in a 65-nm CMOS process, the radiator system occupying a core area of 0.36 mm2 achieves output frequency from 311.6 to 315.5 GHz and maximum equivalent isotropically radiated power (EIRP) of 10.5 dBm while consuming 300 mW. The output phase noise measures −109.3 dBc/Hz at 10-MHz offset and the dc-to-THz efficiency is 0.42%.

Distributed Injection-Locked Frequency Dividers

Abstract: Distributed injection-locked frequency division is introduced as a method to increase the locking range beyond that of conventional injection-locked frequency dividers It is analytically shown that continuous frequency division can be achieved over a frequency range that spans over multiples of the self-oscillation frequency of the core divider Design techniques in millimeter-waves are discussed in detail A proof-of-concept prototype, realized in a foundry 130-nm BiCMOS SiGe HBT technology, achieves a measured locking range of 35–44 and 41–595 GHz while consuming 38 mW from a 115-V supply

Analysis of Phase-Locking in Optoelectronic Microwave Oscillators Due to Small RF Signal Injection

Abstract: In this paper, we analyze the phase-locking phenomenon in a single-loop optoelectronic microwave oscillator, when subjected to the influence of small radio-frequency (RF) signal. We derive the differential equations for the amplitude and phase variations in the oscillator. Using quasi-linear approximation, analytical expressions for the lock range and phase-shift after phase-locking are presented. In addition, beat frequency of the unlocked-driven optoelectronic oscillator (OEO) is obtained and the phase-locking dynamics of the driven oscillator is discussed. Also, the spectrum components of the pulled OEO is derived as a function of the frequency detuning, lock range, beat-frequency, and frequency-shift induced by the phase perturbation of the injection signal. It is shown that all the analytical closed-form expressions clearly demonstrate the phase-locking mechanism starting from the fast-beat state through the quasi-locked state to the locked state of the pulled OEO. Finally, the simulation results are given to validate the analytical results.

A 160-GHz Switched Injection-Locked Oscillator for Phase and Amplitude Regenerative Sampling

Abstract: This letter presents a switched injection-locked oscillator (SILO) operating at 160 GHz. The SILO utilizes positive feedback in a low-gain amplifier stage to achieve high regenerative gain for phase and amplitude information. The circuit is switched off every symbol period before the oscillator reaches its steady oscillation state to prevent the loss of information, then switched on again to receive the next symbol. This provides a viable solution for energy-efficient amplification in millimeter-wave communication systems, and is the fastest reported circuit of its kind. Fabricated in a 0.13- $\mu \text{m}$ SiGe BiCMOS technology ( $f_{T}=300$ GHz), the chip requires an area of 0.64 mm2 and provides 18.4 dB of regenerative gain, while consuming only 6.6 mW of dc power in SILO operation, thus outperforming amplifiers in this frequency range in terms of power consumption.

A 0.015-mm $^{\text{2}}$ Inductorless 32-GHz Clock Generator With Wide Frequency-Tuning Range in 28-nm CMOS Technology

Abstract: This brief illustrates the design of an inductorless high-speed clock generator. Compared to inductance-capacitance ( $LC$ ) oscillators, ring oscillators are used in order to achieve a wide frequency-tuning range with a small chip area. By employing a cascaded phase-locked loop (PLL) architecture, the phase noise of the oscillator can be effectively suppressed. The first PLL is implemented with high-voltage devices under 1.8-V supply to provide a clean reference for the second PLL. The second PLL consists of only low-voltage devices, with a supply voltage of 0.9 V for high-speed operation. Following the second PLL, a clock doubler multiplies the PLL output clock by a factor of 2, which avoids power-consuming high-frequency clock dividers. In order to minimize any mismatch effects, special layout techniques are employed for the second voltage-controlled oscillator and the clock doubler. The prototype chip was fabricated in 28-nm complementary metal oxide semiconductor (CMOS) technology, and it occupies an active area of only 0.015 mm2. The proposed PLL achieves a maximum output frequency of 32 GHz and consumes a total power of 30 mW, exhibiting a power efficiency of 0.9 mW/GHz.

Integer, fractional and side band injection locking of spintronic feedback nano-oscillator to microwave signal

Abstract: In this article we demonstrate the injection locking of recently demonstrated spintronic feedback nano oscillator to microwave magnetic fields at integers as well fractional multiples of its auto oscillation frequency. Feedback oscillators have delay as a new degree of freedom which is absent for spin-transfer torque based oscillators, which gives rise to side peaks along with a main peak. We show that it is also possible to lock the oscillator on its side band peaks, which opens a new avenue to phase locked oscillators with large frequency differences. We observe that for low driving fields, side band locking improves the quality factor of the main peak, whereas for higher driving fields the main peak is suppressed. Further, measurements at two field angles provide some insight into the role of symmetry of oscillation orbit in determining the fractional locking.

Polarization dynamics induced by parallel optical injection in a single-mode VCSEL

Abstract: We report an experimental study of the polarization nonlinear dynamics in a 1550 nm single-mode vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. Experimentally measured stability maps identifying regions of different nonlinear dynamics for various values of bias current are reported. We show that VCSELs with more than a 35 dB polarization mode suppression ratio can have rich nonlinear dynamics in both linear polarizations, including periodic and chaotic behaviors appearing simultaneously in both polarization modes.

Stability analysis of wireless coupled-oscillator circuits

Abstract: Distributed synchronization of sensor networks can be achieved by coupling the oscillator signals of the sensor nodes. Previous works describe the coupling effects in an idealized manner, with constant scalar coefficients. Here a realistic analysis of the coupled-system dynamics is presented for the first time to our knowledge, taking into account the antenna gains and propagation effects on the amplitude and phase values of the equivalent current sources, injecting the oscillator elements. The new formulation provides the synchronized oscillation frequency and amplitude and phase distributions of the coupled system. Distinct oscillation modes, with different phase shifts between the oscillator elements, are identified, associated with the system symmetry. The stability properties of these modes change with the distance between the oscillator elements. The possibility to impose in-phase operation by tuning of the oscillator elements is demonstrated. Good agreement is obtained between simulation and measurements.

Modulation properties enhancement in a monolithic integrated two-section DFB laser utilizing side-mode injection locking method.

Abstract: A monolithic optical injection-locked (MOIL) DFB laser with large stable injection locking range is experimentally demonstrated using the side-mode injection locking technique. The low-frequency roll-off in the MOIL DFB laser is suppressed significantly. The relaxation oscillation frequency is measured to be 26.84 GHz and the intrinsic 3-dB response bandwidth is more than 30 GHz, which is about 20 GHz higher than that of the free running DFB laser. The nonlinear distortions, including the 1-dB compression point, second harmonic distortion (2HD) and third-order intermodulation distortion (IMD3), are also suppressed significantly. A simple radio-over-fiber system transmitting 40 Msymbol/s 32-QAM signal with 6 GHz carrier is achieved using the MOIL DFB laser. After 50 km transmission, the average error vector magnitude (EVM) of the whole link is 2.94% in injection locked state, while the EVM in free running DFB laser is 5.25% as a comparison. To our knowledge, this is the first time that the MOIL DFB laser is realized utilizing the side-mode injection locking method.

42.3 Tbit/s, 18 Gbaud 64 QAM WDM coherent transmission over 160 km in the C-band using an injection-locked homodyne receiver with a spectral efficiency of 9 bit/s/Hz.

Abstract: We demonstrate a 235-channel wavelength division multiplexing (WDM), polarization-multiplexed (pol-mux) 18-Gbaud 64 QAM coherent transmission of 160 km over the full C-band. By applying an injection-locked homodyne detection circuit to WDM coherent transmission, we have achieved low noise optical carrier-phase locking between transmitted data and a local oscillator over the full C-band range. As a result, a potential capacity of 42.3 Tbit/s data with a spectral efficiency of 9 bit/s/Hz was transmitted.

High-Speed Wideband Voltage-Controlled Oscillator via an Injection-Locked Laser

Abstract: We demonstrate a microwave voltage-controlled oscillator able to synthesize a wide range of frequencies in the GHz regime based on an optically injected semiconductor laser. The ability to understand and experimentally characterize the entire injection-locking domain is crucial for the realization and optimization of such a device. This characterization facilitates the identification of steady-state bias conditions, which lead to microwave oscillations. More importantly, it also identifies a regime in which the oscillation frequency can be tuned solely by adjusting the optically injected power, a parameter, which can easily be changed on a nanosecond time scale. In this letter tuning from 6–16 GHz is demonstrated, while tuning rates of ~ $1\times 10^{18}$ Hz/sec are achieved using a < 1 V drive signal, resulting in a voltage-controlled oscillator with rapid tuning speed when compared with conventional, e.g., YIG-based, oscillators.

A Study of Injection Locking in Dual-Band CMOS Frequency Dividers

Abstract: We present a study of dual-band injection locking frequency dividers (ILFDs), based on a nonlinear analysis. We develop a quasi-normal model of these dividers suitable for applying the method of averaging, which allowed us to derive in a simple and expressive manner the first-approximation equations for the amplitudes and phases of the locked modes, both in transient and in steady state. The phase equations have the same form of the Adler’s equation, and represent the generalization of that well-known equation to higher-order frequency dividers. These equations allowed us to derive the locking ranges in a simple explicit form, useful for design purposes. The theoretical results are validated by Spice simulations, and by measurements on a circuit prototype.

Injection Locking and Polarization Switching Bistability in a 1550 nm VCSEL Subject to Parallel Optical Injection

Abstract: We present experimental and theoretical results of bistable polarization switching in a single transverse mode 1550 nm vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. We focus our analysis on the bistability induced by power variation of the master laser found on the recently observed state of simultaneous injection locking of the parallel polarization mode and excitation of the orthogonal polarization mode, IL+PS. Experimental stability maps identifying, in the injected power-frequency detuning plane, where this state is observed, and corresponding bistable regions are reported for several bias currents. We find bistability between the IL+PS state and the single polarization mode injection locked solution. We also find bistability between the IL+PS and different periodic dynamics in the parallel polarization mode. The width of the hysteresis cycle increases when increasing the bias current or when increasing the wavelength of the optical injection beyond the solitary VCSEL wavelength. We theoretically confirm these types of bistability by numerically simulating the spin-flip model and by performing a linear stability analysis for the different stable states. Excellent agreement is found between experimental and theoretical results.

Photonic microwave carrier recovery using period-one nonlinear dynamics of semiconductor lasers for OFDM-RoF coherent detection.

Abstract: This study investigates an all-optical scheme based on period-one (P1) nonlinear dynamics of semiconductor lasers, which regenerates the microwave carrier of an orthogonal frequency division multiplexing radio-over-fiber (OFDM-RoF) signal and uses it as a microwave local oscillator for coherent detection. Through the injection locking established between the OFDM-RoF signal and the P1 dynamics, frequency synchronization with highly preserved phase quality is inherently achieved between the recovered microwave carrier and the microwave carrier of the OFDM-RoF signal. A bit-error ratio down to 1.9×10−9 is achieved accordingly using the proposed scheme for coherent detection of a 32-GHz OFDM-RoF signal carrying 4 Gb/s 16-quadrature amplitude modulation data. No electronic microwave generators or electronic phase-locked loops are thus required. The proposed system can be operated up to at least 100 GHz and can be self-adapted to certain changes in the operating microwave frequency.

Active optical phased array photon integration chip and manufacturing method thereof

Abstract: The invention discloses an active optical phased array photon integration chip and a manufacturing method thereof. The chip comprises a coherent laser array, an optical phase modulator array, a transitional waveguide array and a light field radiation array, wherein the coherent laser array is a master-slave laser realized through a same material and a same technology; through a unidirectional injection locking mode, a plurality of slave lasers possess a same frequency and good coherence of a fixed phase; the optical phase modulator array controls phase delay of each optical phase modulator in the plurality of optical phase modulators to light through an electric signal modulation mode; and the transitional waveguide array and the light field radiation array are used for adjusting wave beams and emission positions of coherent beams which are emitted from different lasers, pass through different optical phase modulators and possess different optical phase delays and determining a coherent superposed light beam emitting direction according to differences of the phase delays. The integration chip can be integrated on a same substrate. Total power of output light is formed by coherent superposition of slave lasers. And the chip possesses advantages of chip integration and high emitting power.

Injection locking of optomechanical oscillators via acoustic waves

Abstract: Injection locking is a powerful technique for synchronization of oscillator networks and controlling the phase and frequency of individual oscillators using similar or other types of oscillators. Here, we present the first demonstration of injection locking of a radiation-pressure driven optomechanical oscillator (OMO) via acoustic waves. As opposed to previously reported techniques (based on pump modulation or direct application of a modulated electrostatic force), injection locking of OMO via acoustic waves does not require optical power modulation or physical contact with the OMO and it can easily be implemented on various platforms. Using this approach we have locked the phase and frequency of two distinct modes of a microtoroidal silica OMO to a piezoelectric transducer (PZT). We have characterized the behavior of the injection locked OMO with three acoustic excitation configurations and showed that even without proper acoustic impedance matching the OMO can be locked to the PZT and tuned over 17 kHz with only -30 dBm of RF power fed to the PZT. The high efficiency, simplicity and scalability of the proposed approach paves the road toward a new class of photonic systems that rely on synchronization of several OMOs to a single or multiple RF oscillators with applications in optical communication, metrology and sensing. Beyond its practical applications, injection locking via acoustic waves can be used in fundamental studies in quantum optomechanics where thermal and optical isolation of the OMO are critical.