Showing papers on "Injection locking published in 2013"
TL;DR: A χ(2)-based in-line PSA with a carrier-recovery and phase-locking system for a phase shift keying (PSK) signal and the regeneration of non-linear impairments induced by fiber non- linearity is demonstrated.
Abstract: We demonstrate a χ(2)-based in-line PSA with a carrier-recovery and phase-locking system for a phase shift keying (PSK) signal. By doubling the signal phase using a wavelength conversion technique, the carrier was recovered from a PSK signal. The carrier phase was synchronized to a local oscillator using optical injection locking. Phase sensitive amplification with a wide phase sensitive dynamic range of 20 dB was achieved using degenerate parametric amplification in a periodically poled LiNbO(3) (PPLN) waveguide. The phase regeneration effect was examined for a degraded signal by means of constellation analyses and bit-error rate measurements. The in-line PSA also operated successfully as a repeater amplifier in a 160 km fiber link without a power penalty. Finally, we demonstrate the regeneration of non-linear impairments induced by fiber non-linearity.
72 citations
TL;DR: In this paper, the authors combined optical injection and polarization-rotated optical feedback in a semiconductor laser to induce self-referenced periodic output that is widely tunable by simply varying the dc bias points of the system's master and slave.
Abstract: Combining optical injection and polarization-rotated optical feedback in a semiconductor laser can induce self-referenced periodic output that is widely tunable by simply varying the dc-bias points of the system's master and slave lasers. We observed a feedback-induced reduction of the fundamental period-one oscillation linewidth by more than two orders of magnitude relative to the injection-only case. Performance was found to be negatively affected by the interference between the external injection signal and the residual feedback in the same polarization. The nonlinear dynamics of the optically injected semiconductor laser can be used to minimize sensitivity to fluctuations in the operating points. However, the use of the nonlinear dynamics at high oscillation frequencies is limited by the decreasing strength of the interaction between the circulating intracavity optical field and the carrier density.
66 citations
Patent•
20 Dec 2013
TL;DR: In this article, a self-injection locking circuit for sustaining an RF modulated optical signal is described, where the circuit is composed of a self injection locking component (107) having a fiber optic delay line (130) over which a portion of the optical signal propagates and a phase detector (150) coupled to the at least two fiber optic cables and configured to determine a phase difference between the signals propagating over one of the respective fiber optic cable.
Abstract: Aspects of the disclosure relate generally to a circuit (100) for sustaining an radio frequency (RF) modulated optical signal. The circuit may comprise a self injection locking component (107) having a fiber optic delay line (130) over which a portion of the optical signal propagates. The circuit may also comprise a self phase locked loop component (109) having at least two fiber optic cables (120, 140) having different lengths and over which another portion of the optical signal propagates and a phase detector (150) coupled to the at least two fiber optic cables and configured to determine a phase difference between the signals propagating over one of the respective fiber optic cables. The circuit may further comprise a voltage controlled oscillator (110) configured to generate a stable oscillating signal in response to signals generated by each of the self injection locking and self phase locked loop components, the stable oscillating signal being configured to sustain the optical signal.
60 citations
TL;DR: An ultra-low power wake-up receiver for body channel communication (BCC) is implemented in 130 nm CMOS process that achieves a sensitivity of -62.7 dBm at a data rate of 200 kbps while consuming only 37.5 μW from the 0.7 V supply.
Abstract: An ultra-low power wake-up receiver for body channel communication (BCC) is implemented in 130 nm CMOS process. The proposed wake-up receiver uses the injection-locking ring oscillator (ILRO) to replace the RF amplifier with low power consumption. Through the ILRO, the frequency modulated input signal is amplified to the full swing rectangular signal directly demodulated by the following low power PLL-based FSK demodulator. In addition, the energy-efficient BCC link mitigates the sensitivity and selectivity requirements for the receiver, which significantly reduces the power consumption. Furthermore, the auto frequency calibrator (AFC) is adopted to compensate the free running frequency of the ring oscillator which is caused by temperature variation and leakage current. The AFC reuses the PLL-based demodulator to periodically set the free running frequency to the desired frequency without any area overhead. As a result, the proposed wake-up receiver achieves a sensitivity of -62.7 dBm at a data rate of 200 kbps while consuming only 37.5 μW from the 0.7 V supply.
51 citations
TL;DR: In this paper, a dither-free phase-locked loop was proposed for long-term locking to OFCs with comb spacings below the high-power injection locking bandwidth.
Abstract: Many applications of optical frequency combs (OFCs) require manipulation and amplification of individual comb modes, e.g., arbitrary waveform generation, terahertz generation and telecommunications. Extracting individual comb modes can be a challenging task for OFCs with narrow comb mode spacings (100 MHz to 10 GHz) due to the limitations of conventional optical filters. Optical injection locking can address this problem, but-due to the relatively large bandwidth (1 to 10 GHz) required for simple (i.e., without the need for additional feedback loops) and stable locking-can struggle when processing OFCs with sub-GHz comb mode spacings. Here, we present an approach to optical injection locking which incorporates a dither-free phase locked loop that allowed for long-term locking to OFCs with comb spacings below the high power injection locking bandwidth. As a result, we achieved robust injection locking directly to a sub-GHz OFC (250 MHz in our experiments). Optimization of the optical injection power is carried out using detailed phase noise characterization. We achieved an Allan deviation for the frequency variation of the slave laser with respect to the injected comb mode (1 s gate time) down to 9.7 × 10-17 and 4.4 × 10-19 at 1 s and 1000 s averaging times respectively, and a phase error variance of 0.02 rad2 (integration bandwidth of 100 Hz to 500 MHz).
50 citations
TL;DR: In this article, a spin-transfer oscillator was injected to a second-harmonic electrical input signal and measured the relative phase and amplitude of the device output as a function of DC current under steady state conditions.
Abstract: We have injection-locked a spin-transfer oscillator to a second-harmonic electrical input signal and measured the relative phase and amplitude of the device output as a function of DC current under steady-state conditions. The relative phase of the device varies quasi-linearly with DC bias, although the averaged amplitude decreases significantly outside of the spectrally determined locking range. By pulsing the injected microwaves, the time required for the device to phase-lock to the injected signal was measured as a function of microwave amplitude. The locking time varied quasi-linearly over the range of amplitudes studied, with the shortest locking times being a few nanoseconds.
48 citations
TL;DR: In this paper, a photonic system for generation of high quality continuous-wave (CW) sub-THz signals is presented, which consists on a gain-switching-based optical frequency comb generator (GS-OFCG), a two-optical-modes selection mechanism and a n-i-pn-i p superlattice photomixer.
Abstract: We report on a photonic system for generation of high quality continuous-wave (CW) sub-THz signals. The system consists on a gain-switching-based optical frequency comb generator (GS-OFCG), a two-optical-modes selection mechanism and a n-i-pn-i-p superlattice photomixer. As mode selection mechanism, both selective tunable optical filtering using Fabry-Perot tunable filters (FPTFs) and Optical Injection Locking (OIL) are evaluated. The performance of the reported system surpasses in orders of magnitude the performance of any commercially available optical mm-wave and sub-THz generation system in a great number of parameters. It matches and even overcomes those of the best commercially available electronic THz generation systems. The performance parameters featured by our system are: linewidth <;10 Hz at 120 GHz, complete frequency range coverage (60-140 GHz) with a resolution in the order of 0.1 Hz at 120 GHz (10-12 of generated frequency), high long term frequency stability (5 Hz deviation over one hour). Most of these values are limited by the measurement instrumentation accuracy and resolution, thus the actual values of the system could be better than the reported ones. The frequency can be extended straightforwardly up to 1 THz extending the OFCG frequency span. This system is compact, robust, reliable, offers a very high performance, especially suited for sub-THz photonic local oscillators and high resolution spectroscopy.
45 citations
TL;DR: A simulation-based model that can be applied to any oscillator topology under any strength of injected signal and accurately predict the behavior of ILOs with asymmetric lock ranges or those using injection into multiple locations is presented.
Abstract: This paper presents a simulation-based model for the behavior of injection-locked oscillators (ILOs) that can be applied to any oscillator topology under any strength of injected signal. By using the phase domain response (PDR) of an oscillator, the proposed model is shown to accurately predict the behavior of ILOs with asymmetric lock ranges or those using injection into multiple locations. It can also model subharmonic injection locking behavior. The model is validated through comparison with SPICE simulations as well as measured results of a multiplying ILO fabricated in 65-nm CMOS.
44 citations
TL;DR: An injection locking-based pump recovery system for phase-sensitive amplified links, capable of handling 40 dB effective span loss, is demonstrated and enables, for the first time, WDM compatible phase- sensitive amplified links over significant lengths.
Abstract: An injection locking-based pump recovery system for phase-sensitive amplified links, capable of handling 40 dB effective span loss, is demonstrated. Measurements with 10 GBd DQPSK signals show penalty-free recovery of a pump wave, phase modulated with two sinusoidal RF-tones at 0.1 GHz and 0.3 GHz, with 64 dB amplification. The operating power limit for the pump recovery system is experimentally investigated and is governed by the noise transfer and phase modulation transfer characteristics of the injection-locked laser. The corresponding link penalties are explained and quantified. This system enables, for the first time, WDM compatible phase-sensitive amplified links over significant lengths.
41 citations
TL;DR: In this article, a simplified light source at 461 nm for laser cooling of Sr without frequency-doubling crystals but with blue laser diodes was developed, and an anti-reflection coated blue laser diode was used to amplify the laser power up to 110 mW by injection locking.
Abstract: We develop a simplified light source at 461 nm for laser cooling of Sr without frequency-doubling crystals but with blue laser diodes. An anti-reflection coated blue laser diode in an external cavity (Littrow) configuration provides an output power of 40 mW at 461 nm. Another blue laser diode is used to amplify the laser power up to 110 mW by injection locking. For frequency stabilization, we demonstrate modulation-free polarization spectroscopy of Sr in a hollow cathode lamp. The simplification of the laser system achieved in this work is of great importance for the construction of transportable optical lattice clocks.
39 citations
TL;DR: It is found that the bifurcation diagram exhibits both bistable and unstable locked regions and the stable locked regime widens as the linewidth enhancement factor increases.
Abstract: A rate equation analysis on the modulation response of an optical injection-locked quantum cascade laser is outlined. It is found that the bifurcation diagram exhibits both bistable and unstable locked regions. In addition, the stable locked regime widens as the linewidth enhancement factor increases. It is also shown that both positive and negative optical detunings as well as strong injection strength enhance the 3 dB modulation bandwidth by as much as 30 GHz. Finally, the peak in the modulation response is significantly influenced by the optical frequency detuning.
TL;DR: In this paper, the authors proposed a new injection-locked optoelectronic oscillator (OEO) which is locked by a low frequency RF signal and without adding high speed devices.
Abstract: We propose a new injection-locked optoelectronic oscillator (OEO) which is locked by a low frequency RF signal and without adding high speed devices. From a low frequency modulated optical carrier, the injection-locking effect in a Fabry-Perot laser diode is able to generate and selectively amplify one high order harmonic component, which is subsequently injected into a single-loop OEO to lock one of the oscillation modes. This process can improve the injected signal quality and simultaneously implement a single-mode OEO with precise oscillation frequency. In the experiment demonstration, a 20-GHz single-mode OEO locked by a 1-GHz RF signal is obtained. The measured side-mode suppression ratio is 65 dB and the phase noise at 1-kHz frequency offset is -94.7ndBc/Hz.
TL;DR: In this paper, the authors describe a simple experiment with a thermoacoustic oscillator driven by a loudspeaker, which exhibits several aspects of synchronization, such as the synchronization region of leading order around the oscillator's natural frequency f 0 and regions of higher order (around f 0∕2 and f0∕3) measured as functions of the loudspeaker voltage and frequency.
Abstract: Since the pioneering work of Christiaan Huygens on the sympathy of pendulum clocks, synchronization phenomena have been widely observed in nature and science. In this paper, we describe a simple experiment, with a thermoacoustic oscillator driven by a loudspeaker, which exhibits several aspects of synchronization. Both the synchronization region of leading order around the oscillator's natural frequency f0 and regions of higher order (around f0∕2 and f0∕3) are measured as functions of the loudspeaker voltage and frequency. We also show that increasing the coupling between the loudspeaker and the oscillator gives rise under some circumstances to the death of self-sustained oscillations (quenching). Moreover, two additional set of experiments are performed: the first investigates a feedback loop in which the signal captured by the microphone is delivered to the loudspeaker through a phase-shifter; the second investigates the nontrivial interaction between the loudspeaker and the oscillator when the latter a...
TL;DR: In this paper, the injection-locked Fabry-Perot laser diodes (FP-LDs) with front-facet reflectivities of 10% and 35% were used as colorless optical networking unit (ONU) in long-reach passive optical networks (LR-PONs).
Abstract: In this study, we use the injection-locked Fabry-Perot laser diodes (FP-LDs) with front-facet reflectivities of 10% and 35% respectively, as colorless optical networking unit (ONU) in long-reach passive optical networks (LR-PONs). Here, the injection-locked FP-LD is directly modulated at 2.5 Gbit/s on-off keying (OOK) and 10 Gbit/s orthogonal-frequency-division-multiplexing (OFDM) modulations for upstream traffic transmission over 60 km of single-mode fiber (SMF). Different operating parameters for the injection-locked FP-LD to achieve higher data rate transmission are reported.
TL;DR: Experimental results of output power bistability in a vertical-cavity surface-emitting laser under optical injection induced by frequency detuning or power variation of the master laser are presented and standard optical injection locking rate equations are theoretically analyzed.
Abstract: We present experimental results of output power bistability in a vertical-cavity surface-emitting laser under optical injection induced by frequency detuning or power variation of the master laser. An ultra-wide hysteresis cycle of 3.7 nm (473.3 GHz) is achieved through frequency detuning, which is more than 11 times wider than that achieved in the state-of-the-art (37 GHz). Furthermore, the width of injection power induced hysteresis cycle we achieved is as large as 7.3 dB. We theoretically analyzed the hysteresis cycles based on standard optical injection locking rate equations including the interference effect of master laser reflection and found excellent agreement with experimental results.
TL;DR: In this paper, a low-phase-noise and low-power Colpitts quadrature voltage-controlled oscillator (QVCO) was proposed to reduce the phase noise.
Abstract: This letter presents the design and analysis for a low-phase-noise and low-power Colpitts quadrature voltage-controlled oscillator (QVCO). The Colpitts QVCO employs current switching to lower the phase noise, gm enhancement to improve the startup condition in the oscillator core, and device reuse to realize anti-phase injection locking for QVCO operation. The proposed Colpitts QVCO has superior phase noise than cross-coupled LC tank VCO and outperforms conventional QVCO in phase noise, quadrature phase accuracy, and tuning range. The fabricated 0.18 μm CMOS Colpitts QVCO draws 500 μA from a 1.5 V power supply and exhibits a phase noise of -118 dBc/Hz at 1 MHz offset and a quadrature phase error of 0.3° at the center frequency of 488 MHz.
02 Jun 2013
TL;DR: In this article, a fully integrated 283 GHz heterodyne receiver in 65 nm CMOS process is presented, which includes a resistive differential mixer, an intermediate frequency amplifier and a 282 GHz subharmonic injection-locked oscillator.
Abstract: A Fully integrated 283 GHz heterodyne receiver in 65 nm CMOS process is presented in this paper. The circuit includes a resistive differential mixer, an intermediate frequency amplifier and a 282 GHz subharmonic injection locked oscillator. The on-chip oscillator generates a 94 GHz fundamental tone but exploits a 282 GHz third harmonic. An injection signal of 47 GHz (one sixth of the RF frequency) is used to lock the oscillator on a reference. The receiver measured conversion gain is -6 dB for a DC power consumption of 97.6 mW. Simulated noise figure is 38 dB. The chip size is 820 μm × 780 μm including matching networks and DC/RF pads.
02 Jun 2013
TL;DR: In this article, a loop of unidirectionally coupled oscillators to demonstrate high tuning range and output power is proposed, which achieves continuous tuning range of 9.5% at the center frequency of 105GHz with the peak output power of 2.8mW.
Abstract: In this work, a loop of unidirectionally coupled oscillators to demonstrate high tuning range and output power is proposed. To achieve large tuning range, two different tuning mechanisms are simultaneously exploited. First each core oscillator is tuned using a variable capacitor. Next, by controlling the phase/delay between the coupled oscillators, the entire loop dynamics and hence its frequency is tuned. In this paper, we analyze a loop of “n” coupled oscillators using Adler's equation and derive the expression for the maximum tuning range. The proposed system is designed and implemented using four coupled Colpitts VCOs in a 65nm bulk CMOS process. The VCO achieves continuous tuning range of 9.5% at the center frequency of 105GHz with the peak output power of 2.8mW. The circuit consumes 54mW from a 1.2V supply. To the best of our knowledge, this VCO has the highest output power and tuning range among all the CMOS oscillators at or above 100GHz.
TL;DR: A tunable single frequency fiber laser based on Fabry Pérot laser diode (FP-LD) injection locking that can be possibly achieved when stable laser oscillation established after many roundtrips through the FP-LD is proposed and demonstrated.
Abstract: We propose and demonstrate a tunable single frequency fiber laser based on Fabry Perot laser diode (FP-LD) injection locking. The single frequency operation principle is based on the fact that the output from a FP-LD injection locked by a multi-longitudinal-mode (MLM) light can have fewer longitudinal-modes number and narrower linewidth. By inserting a FP-LD in a fiber ring laser cavity, single frequency operation can be possibly achieved when stable laser oscillation established after many roundtrips through the FP-LD. Wavelength switchable single frequency lasing can be achieved by adjusting the tunable optical filter (TOF) in the cavity to coincide with different mode of the FP-LD. By adjustment of the drive current of the FP-LD, the lasing modes would shift and wavelength tunable operation can be obtained. In experiment, a wavelength tunable range of 32.4 nm has been obtained by adjustment of the drive current of the FP-LD and a tunable filter in the ring cavity. Each wavelength has a side-mode suppression ratio (SMSR) of at least 41 dB and a linewidth of about 13 kHz.
TL;DR: In this article, a local oscillator (LO) generation scheme for a 21GHz center-frequency 4-GHz instantaneous bandwidth channelized receiver is presented, where a single 1.33 GHz reference source is used to simultaneously generate 20- and 22-GHz LOs with quadrature outputs.
Abstract: This paper presents a local oscillator (LO) generation scheme for a 21-GHz center-frequency 4-GHz instantaneous bandwidth channelized receiver. A single 1.33-GHz reference source is used to simultaneously generate 20- and 22-GHz LOs with quadrature outputs. Injection locking is used instead of conventional phase-locked loop techniques allowing low-power quadrature generation. A harmonic-rich signal, containing both even and odd harmonics of the input reference signal, is generated using a digital pulse slimmer. Two injection-locked oscillator chains are used to lock on to the 10th and 11th harmonics of the reference signal generating the 20- and 22-GHz quadrature LOs, respectively. The prototype design is implemented in IBM's 130-nm CMOS process, draws 110 mA from a 1.2-V supply, and occupies an active area of 1.8 mm2.
TL;DR: This work finds experimentally and numerically that the low frequency phase noise of the driven oscillator is strongly suppressed in both regimes in the same way, and confirms that such behavior is universal for any periodically driven oscillators near a Hopf bifurcation point.
Abstract: When a driven oscillator loses phase-locking to a master oscillator via a Hopf bifurcation, it enters a bounded-phase regime in which its average frequency is still equal to the master frequency, but its phase displays temporal oscillations. Here we characterize these two synchronization regimes in a laser experiment, by measuring the spectrum of the phase fluctuations across the bifurcation. We find experimentally, and confirm numerically, that the low frequency phase noise of the driven oscillator is strongly suppressed in both regimes in the same way. Thus the long-term phase stability of the master oscillator is transferred to the driven one, even in the absence of phase-locking. The numerical study of a generic, minimal model suggests that such behavior is universal for any periodically driven oscillator near a Hopf bifurcation point.
TL;DR: Coherent beam combination is an effective way to develop high-power lasers with high beam quality and high brightness and the combining efficiency is as high as 95.6% at 10 Hz and 85 A.
Abstract: Coherent beam combination is an effective way to develop high-power lasers with high beam quality and high brightness. Coherent combination of six solid-state lasers based on the technique of mutual injection phase locking by using the natural coherent combination property of corner cube is first investigated. The coherent combination with 15.3 J of output energy, 1.7 mrad of divergent angle is obtained, and the combining efficiency is as high as 95.6% at 10 Hz and 85 A. The far-field profile is flattened protuberance.
TL;DR: In this article, the effects of variable-polarization optical feedback (VPOF) on the polarization switching properties of mutually coupled VCSELs were investigated numerically, and the roles of feedback strength, injection strength, and frequency detuning were discussed.
Abstract: The polarization switching (PS) properties of mutually coupled vertical-cavity surface-emitting lasers (VCSELs) subject to variable-polarization optical feedback (VPOF) are investigated numerically. Two injection schemes, parallel-polarization optical injection (PPOI), and orthogonal-polarization optical injection (OPOI) are considered. The effects of VPOF on PS properties are focused on, and the roles of feedback strength, injection strength, and frequency detuning are also discussed. The outputs in the time domain and the polarization evolution through the representation on the Poincare sphere are further presented to explain the dynamics during the PS process. For PPOI, both VCSELs exhibit similar PS properties, abrupt PS can be observed with the variation of polarizer angle, and are hardly affected by frequency detuning. For OPOI, both VCSELs exhibit mixed polarization for all polarizer angles when without frequency detuning. In particular, frequency detuning induced PS can also be observed for a given polarizer angle, and are affected by the leader-lagged relationship in terms of injection locking effect in mutually coupled VCSELs. These results provide an effective tool to obtain controllable PS in mutually coupled VCSELs, and give more insight into the polarization dynamics.
TL;DR: In this article, an injection-locked long-cavity colorless laser diode with different front-facet antireflection (AR) coatings is employed to perform the wavelength injectionlocked ON-OFF-keying (OOK) data transmission.
Abstract: Long-cavity colorless laser diodes with different front-facet antireflection (AR) coatings are employed to perform the wavelength injection-locked ON-OFF-keying (OOK) data transmission. By changing front-facet reflectance of laser diode from 0.2% to 1.2%, the received OOK data enhance its Q factor by 6.3% and reduces its bit error rate (BER) by more than two orders of magnitude, which benefits from the improved signal-to-noise ratio and extinction ratio by up to 8.0%. Enlarging the injection-locking power from -6 to -3 dBm essentially helps the long-cavity colorless laser diode to promote its receiving power sensitivity from -27.9 to -29.2 dBm at BER of 10-9. However, the similar device with lower AR reflectance shows an opposite trend. The injection-locking-induced enhancement is limited within a frequency region controlled by the injection power, which results from a large disparity between continuous-wave injection and stimulated emission inside the long-cavity colorless laser diode. At same biased current and front-facet reflectance, a higher injection level provides a larger modulation throughput at a cost of decreasing bandwidth. The overinjection causes a limitation on frequency bandwidth of the long-cavity colorless laser diodes with lower front-facet reflectance. The numerical simulations with modified rate equations for the injection-locked long-cavity colorless laser diode with lower front-facet reflectance also elucidate that the transmission degrades distinctly at larger injection powers.
TL;DR: In this article, a high-power, frequency-tunable, external cavity diode laser system near 626 nm is described for laser cooling of trapped 9Be+ ions.
Abstract: We describe a high-power, frequency-tunable, external cavity diode laser system near 626 nm useful for laser cooling of trapped 9Be+ ions. A commercial single-mode laser diode with rated power output of 170 mW at 635 nm is cooled to ≈−31°C, and a single longitudinal mode is selected via the Littrow configuration. In our setup, involving two stages of thermoelectric cooling, we are able to obtain ≈130 mW near 626 nm, sufficient for efficient frequency doubling to the required Doppler cooling wavelengths near 313 nm in ionized Beryllium. In order to improve nonlinear frequency conversion efficiency, we achieve larger useful power via injection locking of a slave laser. In this way the entirety of the slave output power is available for frequency doubling, while analysis may be performed on the master output. We believe that this simple laser system addresses a key need in the ion trapping community and dramatically reduces the cost and complexity associated with Beryllium ion trapping experiments.
Patent•
12 Feb 2013TL;DR: In this article, a phase-locked loop is placed in a low-power mode, and the input to the variable-frequency oscillator is stored before the low power mode is entered.
Abstract: A phase-locked loop is placed in a low-power mode. The input to the variable-frequency oscillator is stored before the low-power mode is entered. Then, when the phase-locked loop is awakened, the previous input to variable-frequency oscillator is held at the input to the variable-frequency oscillator. While the input to variable-frequency oscillator is being held, the phase of the feedback signal is calibrated to the reference signal. Once the phase difference between the feedback signal and the reference signal is minimized, the normal feedback operation of the phase-locked loop is enabled.
TL;DR: A 1645 nm Er:YAG nonplanar ring oscillator, resonantly pumped by a 1470 nm laser diode, is reported, obtained with a slope efficiency of 42.1%.
Abstract: A 1645 nm Er:YAG nonplanar ring oscillator, resonantly pumped by a 1470 nm laser diode, is reported. By using a 0.5%-doped Er:YAG nonplanar ring resonator, a 0.284 W single-frequency laser output at 1645 nm was obtained with a slope efficiency of 42.1%. The beam quality in x and y directions were 1.064 and 1.039, respectively.
Patent•
15 Mar 2013
TL;DR: In this article, a variable phase component of a received modulated signal with a second harmonic injection locking oscillator and a delayed phase-compressed signal were combined to obtain an estimated derivative of the variable phase components.
Abstract: Compressing a variable phase component of a received modulated signal with a second harmonic injection locking oscillator, and generating a delayed phase-compressed signal with a fundamental injection locking oscillator, and combining the phase-compressed signal and the delayed phase-compressed signal to obtain an estimated derivative of the variable phase component, and further processing the estimated derivative to recover data contained within the received modulated signal.
TL;DR: In this article, an explicit formulation for the analysis of coupled-oscillator systems is presented, based on a numerical model of the oscillator elements in free-running regime, obtained with harmonic balance.
Abstract: The use of an external injection-locking source prevents undesired frequency shifts in coupled-oscillator systems. Here an explicit formulation for the analysis of these systems is presented, based on a numerical model of the oscillator elements in free-running regime, obtained with harmonic balance. It demonstrates the opposed effects of oscillator coupling and injection locking in a realistic manner and brings to light the influence of the oscillator characteristics and coupling-network parameters. The explicit expressions provide the minimum injection-locking power required for a full variation of the inter-stage phase shift and enable the locking bandwidth to be fixed or maximized through a suitable choice of the coupling networks. Two different cases are considered: a basic system of three oscillator elements and a general system with any number of elements. In the latter case, the influence of the particular element chosen for the signal injection on the synchronization bandwidth is studied. The stability analysis is based on a perturbation system, which, unlike previous works, relies on a direct analytical calculation of the steady-state solutions, instead of a numerical one. This enables the full coverage of all possible solutions and hence an in-depth understanding of the influence of the coupling network and injection source on the stable phase-shift ranges. The phase noise analysis, applied to the same explicit formulation, demonstrates the injection locking effects and enables the identification of different regions as the offset frequency increases.
TL;DR: In this paper, the authors reported the measurement of this sidemode amplification for a semiconductor laser injection locked to a 250 MHz spaced OFC and found that this amplification can be well suppressed by tuning the frequency difference between the free running laser and the OFC mode it was locked to.
Abstract: Optical injection locking can be used to isolate and amplify individual comb modes from an optical frequency comb (OFC). However, it has been observed that for narrow spaced OFCs (e.g. 250 MHz), the adjacent comb modes are still present in the output of the locked laser. These residual modes experience some amplification relative to the injected signal, however the gain is significantly less than for the locked mode. We report the measurement of this sidemode amplification for a semiconductor laser injection locked to a 250 MHz spaced OFC. It was found that this amplification can be well suppressed by tuning the frequency difference between the free running laser and the OFC mode it was locked to. The sidemode amplification was then investigated numerically by solving the laser rate equations under optical injection. It was found that the main contribution to the sidemode amplification was due to phase modulation induced by the residual comb modes. The detuning dependent suppression occurs due to destructive interference between pairs of equidistant comb modes.