Showing papers on "Injection locking published in 1993"

Optical injection induced polarization bistability in vertical‐cavity surface‐emitting lasers

Abstract: We report the observation of bistable polarization switching in a vertical‐cavity surface‐emitting laser under optical injection. The wavelength dependence of the switching is measured. It is found that this polarization switching is achieved through injection locking where both the wavelength and the polarization of the vertical‐cavity laser are locked to the injected optical signal.

Experimental study of an injection-locked gyrotron backward-wave oscillator.

Abstract: A Ka-band gyrotron backward-wave oscillator (gyro-BWO) experiment has been performed to investigate the phase control, fast tunability, and power capability. Efficient injection locking was accomplished by novel circuit arrangements. Maximum power of 113 kW at -19% efficiency was achieved, showing favorable scaling to still higher powers. Stable voltage tuning bandwidth of 5% at 67 kW peak power was also observed. The measured performance has demonstrated a strong potential of the gyro-BWO for new applications requiring high-power tunable millimeter-wave sources

Squeezed light from injection-locked quantum well lasers.

Abstract: Measurements based on balanced detection demonstrate more than 3 dB photon-number squeezing from a quantum well laser injection locked to a coherent signal. We show that injection locking significantly reduces the photon-number fluctuation by suppressing weak side modes that feature intensity noise far above the standard quantum limit. The measurements also reveal that the photon statistics vary qualitatively with the polarization of the laser field.

PLL design for a 500 MB/s interface

Abstract: When operating pins at high data rates, the key problem is to control timing skews (both on- and off-chip) so data on the pins can be read in a short time. The problem of external skews is solved by a clocking scheme where clock and data signals travel the same distance between the sender and receiver so that there is little skew on the 600-mV/sub pp/ external signals. There are two clocks: one for incoming data (RxClk) and one for outgoing data (TxClk). A PLL (phase-locked loop) generates the properly skewed internal clocks to operate the bus. The PLL consists of one main loop and two fine loops (one each for the receive and transmit clocks). The main loop is a VCO (voltage-controlled oscillator) based second-order loop using a 6-stage, small-swing, differential ring oscillator VCO. It is locked to the incoming RxClk after it is amplified to full CMOS levels. VCO and input clock frequency are halved to allow the phase/frequency detector more time to settle. The fine loop delays the internal clock (relative to the input RxClk) by an amount that causes the sampler to produce high and low outputs with precisely equal frequency, thereby compensating for sampler setup time. >

Tunable transform-limited pulse generation using self-injection locking of an FP laser

Abstract: Wavelength-tunable, near transform-limited pulses have been generated using a Fabry-Perot laser diode coupled to a fiber loop containing a fiber Fabry-Perot resonator (FFPR) and a polarization controller. The ratio of transmitted to reflected light from the loop can be adjusted using the polarization controller. Single-mode operation of the gain-switched laser is achieved by self-injection locking, which is induced by light reflected from the fiber loop. The resulting output pulse has a time-bandwidth product of 0.4 and is tunable over about 15 nm by varying the tuning voltage of the FFPR. >

Small signal analysis of THz optical-frequency conversion in an injection-locked semiconductor laser

Abstract: A theory of terahertz optical-frequency conversion using highly nondegenerate four-wave mixing (FWM) in an injection-locked semiconductor laser is presented, using small-signal analysis. The optical frequency conversion can be realized through the use of cavity-enhanced highly nondegenerate FWM in an injection-locked semiconductor laser in a range of 1-THz detuning frequency between the pump and the probe waves, when the probe frequency is tuned close to one of the resonance modes. The frequency conversion is mainly attributed to the nonlinear gain effect. The maximum bandwidth of the converted signal is increased by shortening the laser cavity length. The frequency conversion efficiency is asymmetrical with respect to both the zero detuning frequency and the resonance mode where the converted signal appears. The theoretical results agree with experiments. >

Optically controlled oscillators for millimeter-wave phased-array antennas

Abstract: An approach for the design of optically synchronized millimeter-wave local oscillators based on a subharmonically injection-locked phase-lock-loop technique is introduced. The experimental results support the desired goal of frequency and phase coherency, phase shift control of millimeter-wave oscillators, and self-oscillating mixing to downconvert a millimeter-wave RF signal. Experimental results and theoretical analysis show the advantages of the proposed approach: large locking range of two subharmonically locked oscillators, lower FM noise degradation, and smaller phase error caused by frequency detuning. >

Dynamic and noise properties of tunable multielectrode semiconductor lasers including spatial hole burning and nonlinear gain

Abstract: A general formalism based on the Green's function method is given for multielectrode semiconductor lasers. The effects of both spatial hole burning and nonlinear gain are included in this formalism. An effective nonlinear gain is introduced by taking into account the influence of the laser structure and the associated distribution of the mode intensity along the cavity length and the frequency and intensity modulation properties of multielectrode semiconductor lasers are studied. A general linewidth expression which includes contributions from spontaneous emission and carrier shot noise is given. It is found that the effective alpha -factor affecting the linewidth is in general different from its counterpart affecting modulation and injection locking properties due to spatial hole burning and nonlinear gain. The linewidth due to various contributions is calculated for both uniform intensity distributed lasers and phase-shifted distributed feedback (DFB) lasers. >

Full 360 degrees phase shifting of injection-locked oscillators

Abstract: A design is presented to produce analog phase shift of 0 degrees to 360 degrees in optically controlled oscillators which are subharmonically injection-locked. The proposed concept was analytically described and experimentally demonstrated by producing 360 degrees of phase shift in an 8-GHz oscillator that is indirect optically injection-locked to a 4-GHz subharmonic frequency. This design concept could eliminate the need for switched delay-line phase shifters in the T/R modules of optically controlled phased array antennas, thus making T/R modules more compact and efficient. >

Injection locking and mode switching of a diode laser with a double phase-conjugate mirror

Abstract: We present the experimental results of efficient and alignment-free injection locking of a 0.8-μm diode laser with a mutually pumped phase conjugator. After the slave laser is injection locked, the reflectivity of the double conjugate mirror decreases considerably. The injection-locked state continued for more than 20 min in spite of a decrease in reflectivity. When the frequency of the injecting beam is resonant to one of the slave laser's modes that does not oscillate in the free-running state, mode switching is observed; i.e., the oscillating mode jumps to a new mode that matches the injecting beam.

An injection locked push-pull oscillator at Ku-band

Abstract: A MESFET push-pull oscillator at Ku-band has been designed and tested. This configuration demonstrated larger subharmonic injection locking range and lower FM noise without using a frequency stabilized dielectric resonator. This oscillator demonstrated significant potential for use in subharmonic optically synchronized local oscillators in phase array. >

Analog study of bifurcation structures in a Van der Pol oscillator with a nonlinear restoring force

Abstract: The injection locking and chaotic transitions in a Van der Pol oscillator with a nonlinear-restoringforce term were investigated in this article via an electronic circuit. Free types of locking processes were differentiated from each other in light of local and global bifurcations. The influences of the nonlinear restoring force on the bifurcation structure were also discussed

The semiconductor laser beyond the locking range of optical injection

Abstract: The voltage of a current-driven optically injected semiconductor laser has been measured. The experiments not only show the well known phenomenon of injection locking but also reveal unprecedented dispersive-like structures around the relaxation oscillation frequencies. Based on the single-mode rate equations a theoretical explanation of both phenomena is given. The dispersive-like structures are shown to be caused by four wave mixing.

All-optical timing extraction with frequency division using a twin-section laser diode

Abstract: All-optical timing extraction from a coded line signal with division of the extracted clock frequency is demonstrated using a single twin-section self-pulsating laser diode. Either the bit-rate clock or a submultiple of the bit-rate clock can be extracted, depending only on the DC biases applied to the self-pulsating laser diode. Timing extraction is carried out for the first time without optical injection locking of the self-pulsating laser diode by the optical data source. >

Phase modulated active antenna

Abstract: The authors demonstrate that an active microstrip antenna consisting of a rectangular patch radiator peripherally loaded with a GaAs MESFET can be operated simultaneously as a signal source and as a phase modulator. The experimental and simulated results presented illustrate the degree to which phase modulation can be obtained by applying variable DC bias to the active antenna in the presence of a fundamental frequency injection locking signal.

Dynamics of optically switched bistable laser diodes in the injection-locked state

Abstract: The dynamical properties of dispersive optical bistability in a semiconductor laser biased from below to above threshold are investigated both experimentally and theoretically. The optical bistability switch-off time is found to decrease continuously from below to above threshold. A fast switch-off in less than 100 ps has been observed when the laser operates in the injection-locked condition.

Temperature compensated oscillator circuit

Abstract: Dual mode oscillator (9), e.g. to be used in a temperature compensated circuit in which during operation at least a first oscillation having a fundamental frequency and a second oscillation having a second frequency occurs, which second oscillation is substantially equal to a, preferably the third, harmonic of the first frequency, both said oscillations generating a first and a second oscillation signal, respectively, that may be combined to generate a signal having a substantially linear temperature dependency, the oscillator (9) comprising an electronic controllable switch (S1) connected in such a way that in a first state the oscillator (9) oscillates in the first oscillation and in its other state the oscillator (9) oscillates in the second oscillation, the oscillator (9) having at least one output supplying alternately said first (f1) and said second oscillation signal (f3).

Effects of noise on transients of injection locked semiconductor lasers

Abstract: Semiconductor laser injection locking transients are analyzed. By adiabatically eliminating the carrier dynamics, a single nonlinear stochastic differential equation is obtained for the relative phase between the master and slave lasors. The corresponding Fokker-Planck equation is used to study the steady-state locked conditions as well as phase transients of the locking process. Noise causes the steady-state relative phase between the master and the slave lasers to be a random variable with a standard deviation of approximately a few degrees for typical injection levels. The standard deviation can be reduced by using a phase detector with a limited bandwidth. The mean locking time in the presence of noise is slightly less than the deterministic prediction. Noise also causes the locked lasers to have a finite probability to momentarily unlock. >

Analog study of bifurcation structures in a Van der Pol oscillator with a nonlinear restoring force.

Abstract: The injection locking and chaotic transitions in a Van der Pol oscillator with a nonlinear-restoringforce term were investigated in this article via an electronic circuit. Free types of locking processes were differentiated from each other in light of local and global bifurcations. The influences of the nonlinear restoring force on the bifurcation structure were also discussed

Effect of optical injection on bias voltage and spectrum of a semiconductor laser

Abstract: The effect of a mild form of optical injection on the bias voltage and optical spectrum of a Fabry-Perot-type AlGaAs laser has been studied. At small frequency detuning between the injection and the injected laser, injection locking is observed. The change in bias voltage, as a function of detuning, is dispersive-like and asymmetric, From the asymmetry, the alpha -parameter of the laser is determined. When the detuning is increased beyond the locking range, the effect of optical injection on bias voltage remains noticeable. Additional dispersive-like structures appear around the relaxation oscillation frequency. In the optical spectrum, four-wave mixing and reduced damping of the relaxation oscillations are observed. >

Spectral stabilization of an InGaAsP semiconductor laser by injection-locking

Abstract: This report presents both experimental and theoretical results about phase-locking and spectral purity transfer by light injection in InGaAsP semiconductor lasers. From an experimental point of view, only a few tens of nanowatts are sufficient to impose the injected beam frequency to the slave laser. To make injection-locking more confortable to study, the master laser frequency noise is reduced by resonant optical coupling to an external cavity. The master laser spectral purity transfer and the stability of the slave laser along the locking range are examined in detail. The spectral purity transfer between a monomode beam and a multimode mode laser is also studied. From a theoretical point of view, the nonlinear evolution of the phase-locking mechanisms over the three injection regimes is fully explained. In the multimode case, the spectral purity transfer is due to the saturation sharing between the spectral components of the gain. In the monomode case, the calculation of the frequency noise spectral density of the slave diode laser injected with a low frequency noise beam shows that the master laser spectral purity is fully transmitted to the slave laser up to a frequency which is proportional to the square root of the injected power. The final section presents two injection-locking based methods for measuring the Henry factor, and a comparison with evaluation from a method independent to injection-locking techniques.

Instabilities of a microcavity laser with a weak injected signal.

Abstract: An external cw laser signal in injected into a microcavity laser, and the dynamics of the resulting coupled oscillator system are studied. By variation of the injection detuning and intensity, interesting nonlinear behavior and injection locking are experimentally observed. A theoretical model of this system based on coupled rate equations and including many-body gain effects is presented and yields good agreement with experiment.

Subharmonic injection locking slot oscillators

Abstract: Synchronisation of monolithically integrated slot osciliators [1] at subharraonics of different order is investigated. With the fourth subharmonic, locking bandwidth up to 750MHz can be achieved at an osculating frequency of 71 GHz. The locking bandwidth, depending on the locking power, has been determined. The influence of a change in locking power against the position of the locking bandwidth has been examined.

A direct optically injection‐locked 2.6‐GHz HBT oscillator

Abstract: Measurements on direct optical injection locking of GaAs/Al0.2Ga0.8As heterojunction bipolar transistor oscillators at 2.65 GHz are reported. An oscillator locking range of nearly 6 MHz has been achieved. Optical tuning by dc light is also observed with a tuning range up to 5 MHz. © 1993 John Wiley & Sons, Inc.

Active antenna phase modulator performance

Abstract: This paper demonstrates experimental and simulated evidence on the extent to which an active microstrip antenna consisting of a rectangular patch radiator peripherally loaded with a GaAs MESFET can be operated as a phase modulator. The results given illustrate that phase modulation can be obtained by applying a variable DC bias to the active antenna in the presence of an injection locking signal. It is shown that the injection locking signal can be applied at the fundamental, second harmonic or at subharmonic frequencies. The pushing characteristics of the active antenna module, together with phase modulation plots and circuit/device sensitivity to injection locking signal magnitude are presented.

Subharmonic optically injection locked oscillator

Abstract: A fundamental or subharmonic optically injection locked oscillator is coupled to a phase locked loop circuit. The injection locked oscillator has two single stage HEMT amplifiers with parallel feedback from the drain of a second transistor to a gate of a first transistor. A feedback resonant network controls the oscillator frequency. A microwave/millimeter wave source modulates a laser diode and the signal from the laser diode is then transmitted via an optical fiber to a PIN photodetector diode. The signal from the photodetector diode is injected into the oscillator at an nth subharmonic of the oscillator frequency. The feedback network may consist of a microstrip gap resonator with two tuning varactors at the ends of the resonator. The phase locked loop includes a balanced mixer used as a phase detector to compare the nth harmonic of the signal from the photodetector diode to the sampled output of the oscillator. The output of the mixer is applied to the varactor diodes after being filtered, and a voltage reference is added to the filtered signal to prebias the varactor diodes to the desired frequency of operation.

Experimental study of the Helmholtz resonance of a violin

Abstract: The violin supports a Helmholtz resonance, acting like a driven, damped harmonic oscillator. The amount of damping can be measured from the width of the response curve, and also from the decay of an undriven oscillator. The phase shift between driver and resonator is also consistent with theory. Shifts in resonant frequency due to changing the aspect ratio of the f hole are measured and found to be in qualitative agreement with a convenient formula for the resonant frequency associated with a long thin aperture.

Phase tuning beyond 180 degrees by injection-locked oscillators

Abstract: A method to give phase tuning beyond 180 degrees using fundamental injection locking is presented in the paper This is particularly useful for phased array antenna phase tuning which, previously, is limited to 180 degrees It is shown that by phase shift accumulation in cascaded injection-locked oscillators, the phase tuning range can go beyond 180 degrees Two injection-locked oscillators cascaded together are used to demonstrate the theoretical prediction, which theoretically can give 360 degrees phase shift In addition, the effect on phase shift due to the locking regions is discussed >

Polarization-control mechanisms by injection in vectorial bistable lasers

Abstract: The all-optical control of the polarization in a vectorial bistable monomode laser by injection with a second laser is analyzed theoretically and performed experimentally. The polarization is shown to switch following either an externally induced rotation or an externally induced inhibition mechanism. The usual theory of scalar-locking phenomena is extended to vectorial systems. We show that there is a single locking range in the induced rotation process occurring for low phase anisotropy values, whereas there are two distinct locking ranges in the induced inhibition process for higher anisotropy values. The theoretical results are in good agreement with experiments realized with 3He–20Ne lasers. By scanning the injected signal frequency, optical gates with high signal-to-noise ratios are experimentally obtained.