Showing papers in "IEEE Photonics Technology Letters in 2002"
TL;DR: In this paper, the coupling of optical waveguides to ring resonators holds the promise of a new generation of switches (modulators) which employ orders of magnitude smaller switching (modulation) voltages (or control intensities).
Abstract: The coupling of optical waveguides to ring resonators holds the promise of a new generation of switches (modulators) which employ orders of magnitude smaller switching (modulation) voltages (or control intensities). This requires a means for voltage (or intensity) control of the coupling between the waveguide and the resonator. Schemes for achieving such control are discussed.
621 citations
TL;DR: This source of quantum-correlated photon pairs based on parametric fluorescence in a fiber Sagnac loop, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks.
Abstract: In this letter, we present a source of quantum-correlated photon pairs based on parametric fluorescence in a fiber Sagnac loop. The photon pairs are generated in the 1550-nm fiber-optic communication band and detected with InGaAs-InP avalanche photodiodes operating in a gated Geiger mode. A generation rate > 10/sup 3/ pairs/s is observed, which is limited by the detection electronics at present. We also demonstrate the nonclassical nature of the photon correlations in the pairs. This source, given its spectral properties and robustness, is well suited for use in fiber-optic quantum communication and cryptography networks.
326 citations
TL;DR: In this article, the pump and probe signals are tuned to different resonance wavelengths of the microring and the probe beam is switched in and out of resonance in a pump-and-probe configuration.
Abstract: In this paper, we demonstrate all-optical nonlinear switching in compact GaAs-AlGaAs microring resonators at the 1.55-/spl mu/m wavelength. Switching is accomplished in the pump-and-probe configuration in which the pump-and-probe signals are tuned to different resonance wavelengths of the microring. Refractive index change in the microring due to free carriers generated by two photon absorption is used to switch the probe beam in and out of resonance. Measured transient responses of the pump and probe through the microring show good agreement with theoretical predictions based on nonlinear pump-probe interaction due to two photon absorption.
247 citations
TL;DR: In this article, the spatial resolution of Brillouin strain sensing was improved by the correlation-based continuous-wave technique, which is applicable to smart structures or materials as a nervous system to monitor strain distribution.
Abstract: This letter describes improvement in the spatial resolution of distributed fiber Brillouin strain sensing by the correlation-based continuous-wave technique, which we proposed previously. The spatial resolution of 1 cm has been achieved for a partly stretched fiber. This result shows the technique is applicable to smart structures or materials as a nervous system to monitor strain distribution.
221 citations
TL;DR: In this paper, a cross-gain modulation of semiconductor optical amplifiers has been proposed and demonstrated successfully at 10 Gb/s for all-optical XOR gates.
Abstract: The novel design of an all-optical XOR gate by using cross-gain modulation of semiconductor optical amplifiers has been suggested and demonstrated successfully at 10 Gb/s. Boolean AB~ and A~B of the two input signals A and B have been obtained and combined to achieve the all-optical XOR gate. No additional input beam such as a clock signal or continuous wave light is used in this new design, which is required in other all-optical XOR gates.
215 citations
TL;DR: In this paper, the authors synthesized Ge-As-Se and Ge-S-Se chalcogenide glasses with optical nonlinearities greater than 500 times that of fused silica and figures of merit for all-optical switching >5 at 1.25 and 1.55 /spl mu/m.
Abstract: We have synthesized Ge-As-Se and Ge-As-S-Se chalcogenide glasses designed to have large optical nonlinearities. Measurements reveal that these glasses offer optical Kerr nonlinearities greater than 500 times that of fused silica and figures of merit for all-optical switching >5 at 1.25 and 1.55 /spl mu/m.
213 citations
TL;DR: Tunable, vertically coupled InP microdisk resonant filters having a p-i-n active region and utilizing free carrier injection (FCI) to alter the index of refraction are presented for the first time in this article.
Abstract: Tunable, vertically coupled InP microdisk resonant filters having a p-i-n active region and utilizing free carrier injection (FCI) to alter the index of refraction are presented for the first time. The fabricated devices allow single-mode operation and exhibit a large free spectral range (FSR=10 nm) with high Q values of 7000. Tuning of the resonant characteristics by free carrier injection is demonstrated. The resonant wavelengths of the disk cavity blue-shifts at a rate of 1 nm/mA.
200 citations
TL;DR: In this article, the authors proposed a new concept to produce switchable multiwavelength oscillations with a cascaded fiber Bragg grating overlapping cavity erbium-doped fiber laser.
Abstract: We propose a new concept to produce switchable multiwavelength oscillations with a cascaded fiber Bragg grating overlapping cavity erbium-doped fiber laser. The laser can be designed to operate in multiwavelength or in wavelength switching modes. The different lines have different thresholds. For three-wavelength oscillation, the output powers are linear or piecewise linear functions of the input pump power. An output with a variation of only 1.5 dB has been achieved with an input pump power of 100 mW. For wavelength switching, three single-wavelength and two dual-wavelength operation regions have been obtained toy adjusting the input pump levels.
197 citations
TL;DR: In this paper, a double ring resonator coupled laser (DR-RCL) was proposed and analyzed to achieve a wavelength tuning enhancement of /spl sim/10 dB/cm in the ring resonators.
Abstract: A double ring resonator coupled laser (DR-RCL) is proposed and analyzed in this letter. Benefiting from the uniform peak transmission, narrow bandwidth and other superior characteristics of traveling wave supported high-Q resonators, DR-RCLs offers many promising advantages over the conventional tunable lasers, including ultra wide wavelength tuning range, high side mode suppression ratio, uniform threshold and efficiency, narrow linewidth, low frequency chirp, and simple fabrication. A DR-RCL with a moderate optical loss /spl sim/10 dB/cm in the ring resonators can achieve a wavelength tuning enhancement of /spl sim/50. With such a large tuning leverage, DR-RCLs could utilize the electrooptic effects to achieve ultrafast tuning speed with a wide tuning range covering the material gain bandwidth.
192 citations
TL;DR: In this paper, self-assembled InAs quantum-dash (QD) lasers with emission wavelengths between 1.54 and 1.78 /spl mu/m were grown by gas source molecular beam epitaxy.
Abstract: Self-assembled InAs quantum-dash (QD) lasers with emission wavelengths between 1.54 and 1.78 /spl mu/m based on the AlGaInAs-AlInAs-InP material system were grown by gas source molecular beam epitaxy. Threshold current densities below 1 kA/cm/sup 2/ were achieved for 1-mm-long mirror coated broad area lasers with a stack of four QD layers. The devices can be operated up to 80/spl deg/C in pulsed mode and show a high T/sub 0/ value of 84 K up to 35/spl deg/C. In comparison to quantum-well lasers a much lower temperature sensitivity of the emission wavelength was achieved. The temperature shift of /spl Delta//spl lambda///spl Delta/T = 0.12 nm/K is as low as that caused by the refractive index change.
172 citations
TL;DR: In this paper, the authors demonstrate coherent optical spectrum analysis with /spl sim/70dB dynamic range based on a swept-tuned optical local oscillator and a coherent receiver operating in the 1.5/spl mu/m wavelength hand.
Abstract: In this letter, we demonstrate coherent optical spectrum analysis with /spl sim/70-dB dynamic range based on a swept-tuned optical local oscillator and a coherent receiver operating in the 1.5-/spl mu/m wavelength hand. Measurement principles are presented along with high-resolution measurements of distributed feedback laser spectra.
Abstract: We report the development of a novel optical switching technique consisting of a silica microsphere optical resonator coated by a conjugated polymer. A 250-/spl mu/m diameter silica microsphere was coated by dipping into a toluene solution of poly(2,5-dioctyloxy-1,4-phenylenevinylene). The resonator properties were characterized by evanescently coupling 1.55-/spl mu/m light propagating along a stripline-pedestal antiresonant reflecting optical waveguide into optical whispering gallery modes (WGMs) of the microsphere. WGM resonant frequency shifts as large as 3.2 GHz were observed when 405-nm pump light with a power density of /spl sim/10/sup 4/ mW/cm/sup 2/ was incident on the microsphere. The time constant of the observed frequency shifts is approximately 0.165 s, leading us to attribute the frequency shift to thermooptic effects. As microsphere resonators with WGM linewidths less than 2 MHz (corresponding to cavity Q>10/sup 8/) can be easily fabricated, initial measurements indicate that such a system is capable of thermooptically switching the WGM resonant frequency at speeds on the order of 100 ms.
TL;DR: In this article, a flat-gain polarization-independent continuous-wave fiber-optical parametric amplifier with 15 dB gain over a 20-nm bandwidth was demonstrated using two orthogonal pumps.
Abstract: Fiber-optical parametric amplifiers can be rendered polarization-independent by using two pumps with orthogonal polarization states. We have analytically investigated and experimentally demonstrated, for the first time to our knowledge, a flat-gain polarization-independent continuous-wave fiber optical parametric amplifier with 15 dB of gain over a 20-nm bandwidth, by using two orthogonal pumps.
TL;DR: In this article, the authors studied the statistics of polarization-dependent loss (PDL) in optical systems and evaluated its evolution with system length, showing rigorously that within the range of conceivable parameters in optical links, the distribution of PDL is Maxwellian when it is expressed in decibels.
Abstract: In this letter, we study the statistics of polarization-dependent loss (PDL) in optical systems and evaluate its evolution with system length. We show rigorously that within the range of conceivable parameters in optical links, the distribution of PDL is Maxwellian when it is expressed in decibels. The accumulation of the mean-square PDL with system length stays linear in most systems, but may assume an exponential growth in very long systems with large PDL. The analytical results are compared with numerical simulations and an excellent agreement is observed.
TL;DR: In this paper, an architecture for photonic arbitrary waveform generation where the phase-locked longitudinal modes of a 12.4 GHz fundamentally modelocked external cavity semiconductor laser are individually modulated was proposed.
Abstract: We propose an architecture for photonic arbitrary waveform generation where the phase-locked longitudinal modes of a 12.4-GHz fundamentally modelocked external cavity semiconductor laser are individually modulated. We report photonic synthesis of microwave tones at 37.2 GHz (limited by photodetector bandwidth) with linewidth < 100 Hz and dynamic range 50 dB at 100-Hz resolution bandwidth. We show photonically synthesized 12.4-GHz sine waves with superimposed sinusoidal and pulsed RF modulations, demonstrating the potential for photonic arbitrary waveform generation with the proposed architecture.
TL;DR: In this paper, a Holey fiber with very complex hole geometry is studied by means of a numerical simulator for modal analysis based on the finite element method (FEM) and the results show a good agreement with experimental ones reported in literature.
Abstract: A holey fiber (HF), having very complex hole geometry, is studied by means of a numerical simulator for modal analysis based on the finite-element method (FEM). Polarization and dispersion properties as well as the full vector field distribution of the fundamental mode are investigated. The obtained numerical results show a good agreement with experimental ones reported in literature.
TL;DR: By using optical injection near the transparency wavelength of semiconductor optical amplifiers, the authors in this paper showed that both the saturation output power and the gain recovery can be greatly improved.
Abstract: By using optical injection near the transparency wavelength of semiconductor optical amplifiers, we show experimentally that both the saturation output power and the gain recovery can be greatly improved. By injecting 80 mW of pump power, we observe a 3-dB increase in saturation output power. For 73 mW of pump power, we find a reduction in gain recovery time from over 200 ps down to below 40 ps, while maintaining 14 dB of fiber-to-fiber gain at 1555-nm wavelength.
TL;DR: In this paper, a reduction in linewidth enhancement factor due to the discreteness of the electron states in quantum dots is attributed to the reduction of the linearly-enhanced electron states.
Abstract: Conversion efficiency to longer wavelengths in four-wave-mixing-based wavelength conversion in optical semiconductor amplifiers is generally much lower than that in the opposite direction. This study demonstrates experimentally that this feature is drastically improved, and the asymmetry between conversion directions is eliminated by using quantum dots in the active layer. We attribute this to a reduction in linewidth enhancement factor due to the discreteness of the electron states in quantum dots.
TL;DR: In this paper, a high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot laser with high-to-lowthreshold T/sub 0/ = 213 K (196 K CW) was demonstrated.
Abstract: P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.
TL;DR: In this paper, a highly birefringent air-guiding photonic crystal fiber which provides guidance by a full two-dimensional photonic bandgap (PBG) effect is proposed.
Abstract: A highly birefringent air-guiding photonic crystal fiber which provides guidance by a full two-dimensional photonic bandgap (PBG) effect is proposed. The fiber core is formed by introducing a large air hole that has an area of four unit cells of the cladding materials. It is shown from computed results by a full-vector finite element method that the proposed PBG fiber has birefringence of the order of 10/sup -3/.
TL;DR: In this paper, the authors reported efficient photonic reception of nanowatt microwave signals by their direct upconversion into optical domain using high-Q whispering gallery modes in a millimeter size toroidal cavity fabricated from LiNbO/sub 3.
Abstract: We report efficient photonic reception of nanowatt microwave signals by their direct upconversion into optical domain using high-Q whispering gallery modes in a millimeter size toroidal cavity fabricated from LiNbO/sub 3/.
TL;DR: In this article, the authors presented a novel scheme of up-converting optical intermediate frequency (IF) signals with an optical local oscillator (LO) signal using cross-gain modulation in a semiconductor optical amplifier.
Abstract: The authors present a novel scheme of up-converting optical intermediate frequency (IF) signals with an optical local oscillator (LO) signal using cross-gain modulation in a semiconductor optical amplifier. This scheme provides high conversion efficiency and is independent of the incident light wavelength and polarization. It can be useful for radio-on-fiber transmission system applications in which one remote LO signal is provided for several wavelength-division-multiplexing IF signals.
TL;DR: A depth-first search algorithm is used to generate two-dimensional codes with unit auto- and cross-correlation properties for wavelength-time optical code-division multiple access (CDMA) systems, and it is shown that 2D wavelength- time optical CDMA systems should use codes with low weight and a high wavelength to time chip ratio.
Abstract: In this letter, we use a depth-first search algorithm to generate two-dimensional (2D) codes with unit auto- and cross-correlation properties for wavelength-time optical code-division multiple access (CDMA) systems. We examine how the code weight and size (number of wavelengths and/or time chips) affect the two important system parameters, namely the error probability (bit-error rate) in terms of multiuser interference and the maximum number of codes that can be generated. We show that 2D wavelength-time optical CDMA systems should use codes with low weight and a high wavelength to time chip ratio. The depth first search algorithm allows us to generate significantly more codes than previously proposed code construction algorithms; when used in conjunction with forward error correction, our approach potentially allows for a large number of simultaneous users operating with a BER<10/sup -9/.
TL;DR: In this article, a resonant-cavity-enhanced Si photodetector was fabricated on a reflecting silicon-on-insulator (SOI) substrate.
Abstract: We report a resonant-cavity-enhanced Si photodetector fabricated on a reflecting silicon-on-insulator (SOI) substrate. The substrate incorporates a two period distributed Bragg reflector (DBR) fabricated using a commercially available double-SOI process. The buried DBR provides a 90% reflecting surface. The resonant-cavity-enhanced Si photodetectors have 40% quantum efficiency at 860 nm and response time of 29 ps. These devices are suitable for 10-Gb/s data communications.
TL;DR: In this paper, the authors describe a novel configuration for a wavelength selectable laser that provides wide tuning and distributedfeedback (DFB) performance and reliability at a fundamentally low cost structure.
Abstract: The authors describe a novel configuration for a wavelength selectable laser that provides wide tuning and distributed-feedback (DFB) performance and reliability at a fundamentally low cost structure. The configuration consists of a DFB laser array and a micromechanical mirror that selects one element of the array. The MEMS tilt mirror also loosens the tolerances, since the fine optical alignment is done electronically. Only one laser is operated at a time, with coarse tuning realized by selecting the correct laser and fine tuning by adjusting the chip temperature. The 33-nm total tuning at 20-mW fiber coupled power is obtained in a fully functional module.
TL;DR: In this article, a double-transfer technique using excimer laser liftoff and Pd-In transient-liquid phase bonding was used to transfer a light-emitting diodes (LEDs) fabricated on a sapphire growth substrate.
Abstract: (In,Ga)N light-emitting diodes (LEDs) fabricated on a sapphire growth substrate were successfully integrated onto Si substrates by a double-transfer technique using excimer laser liftoff and Pd-In transient-liquid-phase bonding. This transfer method resulted in a bonded LED heterostructure with the same orientation (p-side up) as the heterostructure before transfer from the sapphire growth substrate. Such a layer transfer approach enables a top and backside contact metallization scheme that reduces device series resistance, current crowding, and top electrode coverage area. Enhancement of the performance of the transferred LEDs was found in terms of the threshold voltage (at 20 mA) and the electroluminescence output from the front surface.
TL;DR: In this paper, a low-loss ultrasmall corner mirrors and T-branches on thin silicon-on-insulator material system were designed and fabricated to demonstrate the potential of this highrefractive-index-contrast material system for high-density planar optical integrated circuits.
Abstract: In this letter, we have designed and fabricated low-loss ultrasmall corner mirrors and T-branches on thin silicon-on-insulator material system. The measured performance of the devices agrees with simulations using finite-difference time-domain calculations. These devices demonstrate the potential of this high-refractive-index-contrast material system for high-density planar optical integrated circuits.
TL;DR: Accumulated packet bit-error-rate measurements confirm the successful error-free packet routing with all-optical label-swapping.
Abstract: This letter discusses an experimental demonstration of a rapidly switching all-optical packet routing system with optical-label switching and all-optical label-swapping capabilities. The optical routing system optically extracts the subcarrier optical-label content, compares it against the forwarding table, makes packet forwarding and label-swapping decisions, and forward the packet to the desired output with a newly updated subcarrier optical label. The packet switching fabric included a combination of rapidly tunable wavelength conversion and a uniform-loss cyclic frequency 8/spl times/8 arrayed waveguide grating router. The packet routing system achieved 600-ps switching time and 250-ns forwarding decision time. Accumulated packet bit-error-rate measurements confirm the successful error-free packet routing with all-optical label-swapping.
TL;DR: In this article, the authors demonstrate a simple technique for dispersion monitoring by adding a single inband subcarrier tone to the transmitted data signal, and demonstrate a measurable dispersion of up to 1200 ps/nm in a 10-Gb/s channel using a 7-9 GHz sub-carrier.
Abstract: In this letter, we demonstrate a simple technique for dispersion monitoring by adding a single inband subcarrier tone to the transmitted data signal. A measurable dispersion of up to 1200 ps/nm is demonstrated in a 10-Gb/s channel using a 7-9 GHz subcarrier and the addition of the subcarrier induced a power penalty of <0.5 dB. Dynamic ranges exceeding 20 dB and resolution sensitivities better than 10 (ps/nm)/dB are shown. With an 8-GHz tone and a 15% modulation depth for 10-Gb/s signals, we show a measurement range of 975 ps/nm with a 22-dB dynamic range. We used the monitor output signal to achieve accurate tunable dispersion compensation.
TL;DR: In this paper, the authors demonstrate a five-element true-time-delay (TTD) system that uses only a single tunable linear chirped fiber grating (TLCFG) delay line for continuous TTD beamforming.
Abstract: In this letter, we demonstrate a new five-element true-time-delay (TTD) system that uses only a single tunable linear chirped fiber grating (TLCFG) delay line for continuous TTD beamforming. The system avoids the complicated wavelength tuning and synchronal control of the tunable lasers as well as the tunable bandpass filters. Different time delays are achieved by tuning the chirp rate of the TLCFG, to which a multiwavelength laser source that carries the RF signal is applied. The time delay responses of the TTD system are measured experimentally, which agree well with the theoretical analysis. The beampointing angle can be controlled continuously by changing the chirp rate of the TLCFG. The minimum time delay step can be much smaller than 1 ps thanks to the high position resolution of the actuator.