Showing papers on "Injection locking published in 1996"

Optoelectronic oscillator for photonic systems

Abstract: We describe a novel photonic oscillator that converts continuous-light energy into stable and spectrally pure microwave signals. This optoelectronic oscillator (OEO) consists of a pump laser and a feedback circuit including an intensity modulator, an optical-fiber delay line, a photodetector an amplifier, and a filter. We present the results of a quasi-linear theory for describing the properties of the oscillator and their experimental verifications. Our findings indicate that the OEO can generate ultrastable, spectrally pure microwave-reference signals up to 75 GHz with a phase noise lower than -140 dBc/Hz at 10 KHz. We show that the OEO is a special voltage-controlled oscillator with an optical-output port and can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and a phase-locked loop. Other OEO applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb frequency and pulse generation, carrier recovery, and clock recovery.

Enhancement of modulation bandwidth of laser diodes by injection locking

Abstract: In this letter, we suggest a new method for significantly enhancing the intrinsic bandwidth of a laser diode through the use of an injection locking technique. Our analysis shows that for moderate and high-injection levels, the bandwidth of a laser diode can be increased to several times its free-running bandwidth.

Small-signal analysis of modulation characteristics in a semiconductor laser subject to strong optical injection

Abstract: Injection locking of a semiconductor laser can induce major changes in the modulation characteristics of the laser. A small-signal analysis using the lumped element model shows that both the frequency and damping of the characteristic resonances of the coupled complex field and free carriers (gain medium) are modified. The detuning between the injected field and the free-running oscillating field, the amplitude of the injection field relative to the free-running field, the linewidth enhancement factor, the cavity photon and spontaneous carrier decay rates, and the field enhancement of the decay rate are all key parameters in determining the changes to the modulation characteristics. For a broad range of parameters, there is simultaneous enhancement of the modulation bandwidth and stable, locked operation. The enhancement is a cavity phenomena and does not occur in a traveling wave amplifier. It requires that the frequency of the locking field be detuned from the injection-modified frequency of the cavity resonance. This causes a resonant enhancement of the modulation sideband associated with the preferred frequency of the optical cavity. Bandwidth enhancements beyond the free-running laser limit are possible over a range of injection levels and injection frequency detunings.

Injection locking dynamics of vertical cavity semiconductor lasers under conventional and phase conjugate injection

Abstract: Stable phase locking of an electrically pumped vertical cavity surface-emitting semiconductor laser (VCSEL) was demonstrated experimentally by injecting light from an edge-emitting master laser into the slave laser VCSEL cavity within a large detuning range (/spl sim/80 GHz). By varying the injected power and frequency detuning, a variety of interesting nonlinear behavior was observed. A theoretical model based on two-field rate equations is presented and compared with experiment, showing good agreement.

Effect of relatively strong light injection on the chirp-to-power ratio and the 3 dB bandwidth of directly modulated semiconductor lasers

Abstract: This paper describes a theoretical study of the small-signal modulation behavior of an injection-locked semiconductor laser. Illustrative examples are given, shelling a comparison between the free-running laser and the same laser with light injection. The results show that a substantial reduction of the chirp-to-power ratio (CPR) can be obtained, depending on both the injection level and the frequency detuning between the master and slave lasers. The behavior of the intensity modulation responses is also investigated, with the modulation conditions chosen in the dynamically stable locking range. It appears that the injection-locked laser may present a larger resonance frequency or modulation bandwidth with respect to those of the same laser under free-running operation.

Microwave signal generation with optical injection locking.

Abstract: Two single-mode laser diodes have been injection locked to the +1 and −1 diffracted orders of a 4.6-GHz acousto-optical modulator. The measured locking bandwidth was 3 GHz for a locking gain of 35 dB. The microwave signal at 9.2 GHz had a measured linewidth of less than a few hertz. We used this system to drive stimulated Raman transitions between the cesium ground-state hyperfine levels. We observed Ramsey fringes and used them to characterize the microwave signal phase noise.

Intensity-noise properties of injection-locked lasers.

Abstract: We present experimental results that illustrate how laser intensity noise near the quantum-noise limit is transferred in an injection-locked cw Nd:(yttrium aluminum garnet) nonplanar ring-oscillator laser. We show that these results are in extremely good agreement with our quantum-mechanical model describing the injection locking process [T. C. Ralph, C. C. Harb, and H.-A. Bachor, Phys. Rev. A]. Three regions in the intensity-noise spectrum are identified and we show that different minimum noise levels exist in these regions. Finally, we show that the injection-locked laser can generate and preserve nonclassical states. \textcopyright{} 1996 The American Physical Society.

High-performance heterodyne optical injection phase-lock loop using wide linewidth semiconductor lasers

Abstract: The requirements for narrow linewidth lasers or short-loop propagation delay limit optical phase-lock loop realizability with semiconductor lasers. Although optical injection locking can provide low-phase-error variance, its locking range is limited by stability considerations. The first experimental results for an heterodyne optical injection phase-lock loop are reported. Phase-error variance as low as 0.003 rad/sup 2/ in a bandwidth of 100 MHz, single-sideband (SSB) noise density of -94 dBc/Hz at 10-kHz offset and mean time to cycle slip of 3/spl times/10/sup 10/ s have been achieved using DFB lasers of 36-MHz summed linewidth, a loop propagation delay of 20 ns and an injection ratio of -30 dB.

A new measurement approach for phase noise at close-in offset frequencies of free-running oscillators

Abstract: This paper presents a new measurement approach which has been developed as a practical method for quick, accurate and low cost measurements of close-in offset phase noise of microwave free-running oscillators. To overcome the shortcomings of conventional measurement methods, this approach utilizes the injection locking technique to stabilize the free-running oscillator and down-convert the oscillator noise to baseband. Theoretical and experimental studies clearly demonstrate the accuracy, the effectiveness and the flexibility of this measurement technique. The phase noise of voltage controlled oscillators (VCO's) at 2.5 and 9.3 GHz have been measured to verify the new approach.

Optical control of 14 GHz MMIC oscillators based on InAlAs/InGaAs HBTs with monolithically integrated optical waveguides

Abstract: An In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As heterojunction bipolar transistor (HBT) with a novel integrated optical waveguide for light input has been developed. Detailed modeling is used to validate the design and simulate the coupling of light from the waveguide into the device. Fabricated waveguide-HBT devices exhibited cutoff frequencies of f/sub T/=32 GHz and f/sub max/=48 GHz with 56% of the guided light being converted to photocurrent. Fabricated MMIC oscillators operating at 13.9 GHz exhibited direct optical controllability in the form of optical tuning and injection locking. This is the highest reported frequency for direct optical injection locking in an HBT-based oscillator.

Injection locking of a passively mode-locked laser

Abstract: We present and analyze a model of a passively mode-locked laser, which is subjected to injection of a coherent pulse train. The model, based on soliton perturbation theory, predicts the possibility of coherent injection locking, and gives analytical estimates for the locking ranges. The ability to simultaneously lock the timing and the phase of the output pulses of a mode-locked laser to an injected, coherent pulse train is shown. The interesting limiting case of phase locking the mode-locked laser to a constant amplitude external injection, is addressed with implications for future coherent soliton communication systems.

A SIMMWIC 76 GHz front-end with high polarization purity

Abstract: An integrated active antenna with a polarization purity better than 28 dB and a radiated power of 8 dBm at 75.7 GHz is presented. The linearly polarized radiator consists of a planar resonant antenna and a transit-time diode monolithically integrated on a silicon substrate. This active antenna finds various applications in low-cost multi-channel sensor systems, e.g. for object classification. Guidelines for the design are discussed. The characterization of the fabricated SIMMWIC devices includes measurements of output power, polarization purity, and far-field pattern. Moreover, the oscillation frequency of the devices has been successfully stabilized using subharmonic injection locking. The FM noise behavior of the locked oscillator has been characterized. The measured results are presented and compared to theoretical calculations.

Theory of laser-amplifier injection locking

Abstract: The theory of the laser amplifier is developed for conditions in which the strength of the input signal is increased from small values, where the amplification is linear, to larger values, where the amplification becomes nonlinear. The below-threshold laser amplifier oscillates at a single frequency equal to that of the input signal, and its properties are found by solution of the nonlinear equation of motion for the single excitation amplitude. For the above-threshold laser amplifier, the effects of the nonlinear behavior are to shift the laser frequency from its free-running value and to transfer intensity from the laser line to the signal frequency and to a range of satellite lines, whose frequency detunings are integer multiples of the signal detuning. The intensities of the various emission lines of the laser are calculated by power-series expansions of the field amplitudes up to terms of fourth order in the input signal strength. The onset of injection locking is determined by the conditions for which the intensity at the shifted free-running laser frequency falls to zero. The injection-locked state is characterized by a single excitation frequency equal to that of the input signal, and its properties are found by solution of the same nonlinear equation of motion as for the below-threshold amplifier. The ranges of input signal strength and detuning are determined for which the injection-locked state is stable. The energy conservation properties of the laser amplifier are considered for each of its operating states. \textcopyright{} 1996 The American Physical Society.

Noise effects in injection locked laser simulation: phase jumps and associated spectral components

Abstract: Some clarifying simulation results concerning the effect of noise on injection locking are presented and analysed. A new spectral component near the eigenfrequency, associated with discrete phase jumps, is observed on the injected laser spectrum. This phenomenon, not appreciable if the noise is not taken into account, has also been observed in recent experimental works, with very similar reported results.

Optical control of resonant tunneling diode monolithically integrated with PIN photodiode

Abstract: Optical control of the resonant tunneling characteristics of an integrated optoelectronic device with a monolithic integrated double-barrier/PIN structure is studied. Optical switching of the bistable resonant tunneling state and optical injection locking of a resonant tunneling oscillator at 1 GHz are demonstrated.

A novel 75 GHz InP HEMT dynamic divider

Abstract: A novel dynamic frequency divider IC is realized by injection locking a broadly tunable push-pull oscillator. The injection locking process is explained using a simple pumped-delay model of a two-stage ring oscillator. Two different dynamic dividers were fabricated in the Hughes 0.1 /spl mu/m gate-length InP HEMT process. The first covers 15-68 GHz while the second operates over the entire band from 50 to 75 GHz.

A model of injection-locked relativistic klystron oscillator

Abstract: By the use of a simple model, we explicitly incorporate the coupling between the driver cavity and the booster cavity in a relativistic klystron amplifier (RKA). We show that this RKA configuration may turn into an injection-locked oscillator only when the beam current is sufficiently high. Other features revealed by this model include: the downshifted frequency mode ("0" mode) is unstable whereas the upshifted frequency mode ("/spl pi/" mode) is stable; the growth rate of the "0" mode is relatively mild so that the oscillation can start only in an injection-locked mode; the oscillation does not require the presence of reflected electrons; and the separation of the cavities must be sufficiently short. These, and other features, are found to be in qualitative agreement with the recent experiments on the injection-locked relativistic klystron oscillator (RKO) that were conducted at Phillips Laboratory.

Synchronized two-color operation of a passively mode-locked erbium-doped fiber laser by dual-injection locking

Abstract: Summary form only given. The simultaneous operation of a passively mode-locked laser at two different wavelengths is important as a source for high-pulse-rate, wavelength-division multiplexing (WDM) schemes, for wideband pump probe and four-wave mixing experiments. Using the recently introduced harmonic injection-locking scheme, we achieved synchronized locking of a passively mode-locked fiber laser, at two wavelengths (1.53 /spl mu/m and 1.55 /spl mu/m) simultaneously, producing pulses of several picoseconds with 7.5-GHz pulse repetition rates. Because the same scheme can also serve as a storage ring, this work demonstrates the feasibility of a two-color memory ring.

Injection locking of photonic paint.

Abstract: The narrow-linewidth laser emission from a scattering gain medium can be forced to oscillate in a narrower emission bandwidth with the introduction of a seed in much the same way as the injection-seeding technique used to produce single-mode oscillation from conventional lasers. The system exhibits complete spectral collapse at all wavelengths other than that of the seed and a large enhancement of the isotropic emission peak intensity. A theory explaining the emission characteristics and the minimum threshold seed energy required for locking is presented.

Push-push subharmonically injection-locked oscillator

Abstract: A push-push injection-locked dielectric resonator oscillator has been designed for subharmonically injection-locked local oscillators in phased-array antennas at the K-band and above. This circuit topology has the following advantages: (i) a large subharmonic injection locking range using a dielectric resonator with a high quality factor: (ii) a larger frequency multiplication factor, while a microwave device, such as a MESFET, is operating at a low oscillation frequency and having an effective noise temperature (T/sub eff/) resulting in a reduction in frequency drift over the operating temperature and the intrinsic FM noise of the free-running oscillator: (iii) a higher yield rate in MMIC applications.

Optical bistability in semiconductor lasers under intermodal light injection

Abstract: Optical bistability in semiconductor lasers under intermodal light injection is predicted using small-signal analysis. The optical bistability is a special case of sidemode injection locking and originates from the strong gain nonlinearity introduced by external light injection. The theory can be applied to the optical bistability under both intramodal and intermodal light injection. And the difference of the optical bistabilities between intermodal and intramodal light injection is discussed. Expression for the bistable loop width is presented. Optical frequency-bistability and power-bistability in semiconductor lasers can be realized by intermodal light injection, which imply that a small (a few GHz) change of the injected light frequency or a small (several /spl mu/W) change of the injected light power will induce a large (up to THz) change of the laser emitting frequency. Besides, hybrid optical bistability can be achieved by varying the bias current (only a few mA) of the laser. Dynamic properties, such as turn-on and turn-off delay and carrier overshoot during switching are discussed and some consideration of the practical aspects of the optical switching is presented.

Microstrip and coplanar SiGe-MMIC oscillators

Abstract: We report on design, technology, and experimental results of microstrip and coplanar Si-SiGe HBT Ks-band oscillators integrated monolithically on high resistivity silicon. The tuning range of the microstrip VCO was 100 MHz around 22.8 GHz and the output power reached-7 dBm with a conversion efficiency of 1%. The coplanar LC oscillators reached output powers of up to 1 dBm with a conversion efficiency of 358 at 28.1 GHz and 37.8 GHz. This exceeds the requirements for subharmonic injection locking of transit-time diodes like IMPATT oscillators. With the availability of such HBT oscillators extremely compact and low-cost FMCW radar circuits for use in industrial and traffic sensor systems will become possible in the ISM-bands 24 GHz (direct operation) and 76.5 GHz (by subharmonic injection locking).

Phase coherency of generated millimeter wave signals using fiber optic distribution of a reference

Abstract: The work presented here is focused on analytical comparison of various methods of generating a low phase noise millimeter-wave local signal, from a frequency reference Noise performance requirements of directly and externally modulated fiber optic distribution networks are considered Four techniques of multiplication, phase-locked loop, injection locking, and injection locking with phase locked loop are compared in terms of system figures of merit

A comparison between rate-equation and Fabry-Perot amplifier models of injection locked laser diodes

Abstract: The rate-equation and the Fabry-Perot amplifier models for injection locked laser diodes are compared. Both models give identical results at the limiting case of no injected signal. The Fabry-Perot model predicts a wider locking bandwidth and is more useful for large signal applications. The rate-equation model is suitable for investigating the dynamic properties. Numerical results from both models are presented.

10 GHz all-optical clock recovery using a mode-locked semiconductor laser in a 40 Gbit/s, 100-km transmission experiment

Abstract: Summary form only given. In conclusion, we performed a 40 Gbit/s, 100-km transmission experiment including demultiplexing from 40 Gbit/s to 10 Gbit/s by using a mode-locked semiconductor laser simultaneously as pulse source for the demultiplexer, as all-optical clock recovery, and as detector to synchronize the BER test set.

NOLM oscillator and its injection locking technique for timing clock extraction and demultiplexing

Abstract: A new regeneratively mode-locked opto-electric oscillator, using a nonlinear optical loop mirror (NOLM), is presented. Part of the NOLM output is led to a clock extraction circuit, and the extracted signal is fedback to a gainswitched laser diode which is used as a control pulse. When a CW input beam is coupled into the NOLM, the electro-optic feedback circuit initiates the pulse oscillation. The authors generated a 9 ps optical pulse train at 10 GHz.

Noise in pulsed injection locking of a passively modelocked laser

Abstract: In this paper, noise effects related to pulsed injection locking of a passively modelocked laser (PML) are analyzed. A set of nonlinear equations, derived from a soliton perturbation method, is used to describe the modelocked laser pulse evolution, under injection locking. The equations are linearized, and the stability of the injection locked solution is studied. Subsequently, the linear equations are employed to describe the coupling of both the injected signal noise and the internal noise, to the locked pulses. Noise reduction due to the injection process is demonstrated, with important implications for all optical signal regeneration and synchronization.

Pulse amplification apparatus and method

Abstract: An electromagnetic radiation reflection amplifier capable of amplifying cw or pulsed signals has a pair of cw oscillators (20, 22) operated under injection locking conditions. Diversion of oscillator power to a separate signal path during the off time of the input pulse is achieved through purely passive means; no active control devices are utilized. The device can be implemented for amplification of microwave, millimeter wave or optical signals. The amplifier comprises a 180° hybrid coupler (10), a matched pair of cw oscillator modules (20, 22), a waveguide discontinuity (36), a waveguide termination (26), and an optional signal input element. For a magic-tee hybrid coupler, the cw oscillator modules are mounted on the ports of the symmetrically positioned waveguide arms (16, 17) and the waveguide discontinuity (36) is located within either the sum arm or difference waveguide arm intermediate its ends. The waveguide termination is located at the port (14) of that arm, and the port (11) of the other non-symmetric arm of the magic-tee becomes the input/output port.

Photonic radio frequency synthesizer

Abstract: A photonic radio-frequency synthesizer is proposed in which two or more distributed-feedback laser diodes are injection- locked to different optical modes of an actively-mode-locked external-cavity laser diode. The injection-locked laser outputs are combined to produce a high-stability, low-phase- noise heterodyne optical signal with frequency separation in the 1 GHz through millimeter-wave frequency range that is a multiple of the active mode-locking reference oscillator frequency. Since the phase fluctuations of the individual longitudinal modes of the mode-locked laser are highly correlated, the phase fluctuations of the heterodyne output signal are minimized. This approach yields optical heterodyne signals with widely tunable millimeter-wave frequency separations and low phase noise, without the need for a wideband millimeter-wave electronic reference oscillator and frequency-locking control loop as required in previous heterodyne signal generation schemes.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A simple microwave oscillator photodetector operating with optical signals designed by an illuminated FET model

Abstract: This paper describes modeling for an illuminated self-aligned GaAs MESFET with nonlinear parameters and experimental evaluation of an FET oscillator with non-modulated, CW and pulse signal illumination for optical control, injection locking and digital signal communication