Showing papers on "Injection locking published in 1991"

A 100-MESFET planar grid oscillator

Abstract: A 100-MESFET oscillator which gives 21 W of CW effective radiated power (ERP) with a 16-dB directivity and a 20% DC-to-RF conversion efficiency at 5 GHz is presented. The oscillator is a planar grid structure periodically loaded with transistors. The grid radiates and the devices combine quasi-optically and lock to each other. The oscillator can also be quasi-optically injection-locked to an external signal. The planar grid structure is very simple. All of the devices share the same bias, and they can be power and frequency tuned with a mirror behind the grid or dielectric slabs in front of it. An equivalent circuit for an infinite grid predicts the mirror frequency tuning. The planar property of the oscillator offers the possibility of a wafer-scale monolithically integrated source. Thousands of active solid-state devices can potentially be integrated in a high-power source for microwave or millimeter-wave applications. >

Injection locking in distributed feedback semiconductor lasers

Abstract: Injection locking properties of distributed feedback semiconductor lasers are studied systematically. Due to the high side mode suppression, these devices show different locking properties when compared to lasers with Fabry-Perot structures. The main result is the identification of four regimes for different injection levels. In particular, a symmetrical locking band at low optical injection level is confirmed. The presence of this symmetrical band can be exploited in some applications. As examples, the measurement of the linewidth enhancement factor and the phase-shift-keying modulation capability are reported. >

Modulation properties of an injection-locked semiconductor laser

Abstract: The modulation properties of an injection-locked semiconductor laser are investigated using the rate equation formalism. Intensity and phase modulations (IM and PM) are analyzed throughout the locking range where the locked laser is stable. The relaxation oscillation resonance in the IM and PM frequency responses can be dramatically reduced by tuning the injected power and the frequency difference between the master laser and the free-running slave laser. The power spectra under direct modulation are derived throughout the stable locking range. The spreading of the harmonics of the modulated locked laser is strongly affected by the frequency detuning, the injected power, and the injected current modulation. Measurements illustrating the theoretical results are also presented. >

High-power single-mode diode-pumped Nd:YAG laser using a monolithic nonplanar ring resonator.

Abstract: A 0.91-W single-frequency diode-pumped Nd: YAG laser at 1.06 μm is demonstrated with a TEM00 output. We also report a 60% slope efficiency from another nonplanar monolithic ring laser with diffraction-limited, single-frequency, 1.06-μm output. Injection locking of two 0.17-W monolithic nonplanar ring resonators gave 0.34 W of single-mode power. Actively controlled injection locking of two lasers was demonstrated for indefinite periods.

Analysis of injection-locked gain-guided diode laser arrays

Abstract: A new model for injection-locked gain guided laser arrays is proposed. Diffraction-limited and single-lobe operation of injection-locked arrays is attributed to coherent summation of several transverse modes that are phase locked by injection. The model predicts far-field and near-field patterns, locking bandwidth, beam-steering properties, and locked output power. The effects of varying the master power, beam shape, position, and incidence angle on the slave array facet are also studied. Theoretical and experimental results are compared. >

Two-port FET oscillators with applications to active arrays

Abstract: Investigations of two-port FET oscillators and their use in active arrays for spatial power combining are reported. The two-port oscillator considered consists of a single FET oscillator with distinct input and output ports. This type of oscillator exhibits increased locking bandwidth over alternative approaches. Results are given for a prototype five-element linear array operating at 6 GHz. In this case, the entire array is synchronized by a single injection signal supplied to the first oscillator. The array exhibited a locking bandwidth of greater than 500 MHz with a 0-dBm injection signal. However, the radiation pattern had sidelobe levels below -10 dB for only 300 MHz of this range. Variation of the main lobe with frequency is shown. The main lobe direction variation is about 7% per 100 MHz of frequency change. >

Analysis of a homodyne receiver using an injection-locked semiconductor laser

Abstract: The authors study an optical homodyne receiver using an injection-locked semiconductor laser as a local oscillator. The carrier recovery process introduces a phase error, and the calculation of its statistical properties leads to the evaluation of the receiver performance. The analysis shows the dependence of the receiver performance on the injected power and the phase detuning, between the transmitter, and local oscillator electric fields. The receiver performance is affected by the phase noises of the transmitter and local oscillators, by the shot noise of the detectors in the receiver, and by the modulation noise resulting from the injection locking of the local oscillator by a modulated signal. >

Stable-locking bandwidth in sidemode injection locked semiconductor lasers

Abstract: An analytical expression for the possible sidemode locking bandwidth, consistent with the formula for peak-mode injection locking, is derived. Small-signal analysis is then applied to investigate the stable part of the locking range. The results demonstrate that sidemode injection locking offers relaxed operational requirements for frequency matching, with enhanced bandwidth, while retaining the traditional benefits of injection locking.

CW injection seeding of a modelocked semiconductor laser

Abstract: The authors extended the injection locking technique to control the output of a modelocked semiconductor laser with an external continuous-wave (CW) signal. With this injection seeding technique, over 8 mW of average power in 30 ps pulses with side cluster suppression of over 20 dB was obtained from an actively modelocked AlGaAs semiconductor laser. This average output power compares favorably with the 12 mW W output power of the extended resonator. The frequency spectrum of the laser is determined by the background noise level as set by the spontaneous emission. Injection seeding overrides the noise and concentrates over 99% of the available energy in a single nearly transform-limited pulse. >

A double-stage injection-locked oscillator for optically fed phased array antennas

Abstract: In an optically fed phased array antenna system, the microwave carrier signal is transmitted via a modulated lightwave to each active T/R (transmit/receive) module, where it must be converted back to the microwave domain. Currently, efficient optical-to-microwave conversion is extremely difficult, as the detected microwave signal is weak and noisy. A novel circuit, containing a high-gain/low-noise microwave injection-locked oscillator, has been developed to improve the interface between the optical and microwave components. The circuit utilizes two FETs and a dielectric resonator, which serves as a frequency-dependent feedback element. The circuit, designed to operate at about 8 GHz, provides significant amplitude and phase noise suppression. In addition, the circuit realization is compatible with MMIC technology. >

Injection-locking of Q-switched AlGaAs laser with fast saturable absorber

Abstract: Injection of a weak CW laser beam in a Q-switched AlGaAs laser diode with a fast saturable absorber is shown to produce powerful single-mode picosecond pulses at 082μm The saturable absorber regions are obtained by deep implantation of heavy ions through the diode facets Single-mode operation is achieved with CW injection powers as low as 50μW Peak powers exceeding 15W are detected at the laser output A time-resolved spectroscopy of the laser pulses reveals an overall downchirp of 15nm

Analog frequency divider utilizing two amplifiers and a LC resonant circuit

Abstract: An microwave analog frequency divider capable of ten percent bandwidth at 10 GHz has push-push amplifiers forming an injection locked oscillator. The input frequency f i is injected at the amplifier reference terminals. The amplifier control terminals are coupled by L's and the reference terminals are coupled by C's and the reference and control terminals form with the L's and C's a resonant circuit tuned approximately to the output frequency f o =f i /N, where N is the divisor. Parallel resonant circuits in the f i injection path have high impedance at f o to prevent loading of the oscillator. A control device in the f i injection path turns the oscillator on when f i is present and off when f i is absent. Matching networks are included at input, output and between the control device and the oscillator to obtain efficient operation.

Power-combining and injection-locking magnetrons for accelerator applications

Abstract: The authors are investigating a number of approaches to achieve phase locking and power combining without the use of circulators. In the method described, the X-band waveguide 3 dB hybrid coupler provides the avenue for both injection locking and power combining of magnetron pairs. A series of experiments were undertaken where two magnetrons are injection locked and power combined, first operating into a matched load, then into a tunable short, and finally into X-band cavities. It was observed that injection-locked magnetrons can be used to drive a moderate Q cavity at long pulse without a circulator with excellent phase coherency. The cavity transient impedance does not preclude the magnetrons from filling the cavity, at least when the cavity fill time is less than the magnetron phase lock time. >

Injection locking of a long-pulse relativistic magnetron

Abstract: The authors report the injection locking results of a long-pulse (200-400 ns) high power (20-30 MW) relativistic magnetron. The cold-cathode magnetron structure is driven by a high power modulator to generate S-band output at 3.3 GHz. Phase-locking with reproducible locked angle is achieved with an injection power ratio as low as 1:200. The locked states are phase stable to within +/- 3 degree(s) during the pulse. Repetition-rated operation at 5 Hz produces average powers higher than single shot systems. Phase locking physics is studied by parametrically scanning the injection frequency and varying the injection power. Important effects due to frequency pushing are identified. The measured locking bandwidth agrees well with a theory which takes into account frequency pushing effects. The measured dependence of final locked phase on injection frequency and injection power also agrees well with theory.

Optical response of the GaAs MESFET at microwave frequencies and applications

Abstract: The authors consider the MESFET as an optical port on MMICs (monolithic microwave integrated circuits). It is shown quantitatively how better optical coupling improves the photoresponse of the MESFET. It is pointed out that by modest redesign its frequency response can be significantly extended up to 10 GHz. How these can be converted to better optical control of MMIC circuits is demonstrated. A direct optical injection locking of a MESFET oscillator was performed. The measured optical injection locking bandwidth was 43.8 MHz. >

A direct optical injection locked 8 GHz MMIC oscillator

Abstract: The optical injection locking behavior of a monolithic integrated heterostructure FET (HFET)-oscillator has been investigated. The monolithic integration is an important step towards the implementation of optically controlled oscillators in phased array antenna systems. The oscillator was designed to operate at 8 GHz. The gate and source terminals of the HFET were biased at 0 volt through coplanar lines, which also served as a feedback and resonator circuit. The active region of the device was illuminated by a pigtailed laser diode modulated at about 8 GHz so that the oscillator circuit could be optically injection-locked. The experimental results show the optical locking behavior of the oscillator. A direct comparison between optical and electrical injection locking is possible. >

A circularly polarized FET oscillator active radiating element

Abstract: An FET oscillator that combines the power from three devices and directly generates circularly polarized radiation using a novel feedback arrangement is presented. Because of its transmission type configuration, it exhibits a broad injection locking range. This makes it useful as an element of an active antenna, where several such oscillators would be locked to a modulated signal. The injection locking signal would be orders of magnitude lower than the corresponding drive level for a passive antenna. The radiated field exhibits a minimum axial ratio of 1.04. >

Highly coherent injection-locked laser diode arrays.

Abstract: Two physically separated laser diode arrays were simultaneously injection-locked to the same master laser. The modulus of their mutual coherence function was measured, and the resulting value 0.96 ± 0.06 was close to the maximum allowed value of 1. The spatial phase of the two injection-locked outputs did not vary from each other by more than 0.05 wave (λ/20), apart from a phase difference that grew linearly with position, due to the tilt between the two interfering beams. Requirements for the coherent combination of injection-locked laser diode arrays are discussed.

Coherent pulsed injection seeding of two gain-switched semiconductor lasers

Abstract: High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 AA wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated. >

Inversion in harmonic noise driven bistable oscillators

Abstract: We consider the dynamics in a asymmetrical bistable oscillator driven externally by a noisy harmonic oscillator. The basic for our approach is the energy dynamics in each well of the oscillator in the low friction limit. We discuss the possibility of energy inversion states generated by harmonic noise and show this effect by simulations.

Power scaling in quantum-well laser amplifiers

Abstract: The effects of increasing excitation on the performance of quantum-well semiconductor laser amplifiers were investigated. Amplified spontaneous emission (ASE) and gain roll over at high injected carrier densities are two limitations to the power scaling of these devices. A Rigrod analysis was used to study the effects of these limitations on the gain, ratio of signal to ASE power, and efficiency for different values of injection current, facet reflectivity, and input laser intensity. Comparisons are made with an equivalent amplifier operating with a bulk semiconductor gain medium. This analysis suggests that quantum-well semiconductor amplifier performance improves with a double-pass configuration. >

Analysis of receiver using injection-locked semiconductor laser for direct demodulation of PSK optical signals

Abstract: A receiver for PSK optical signals is analysed. The demodulation is performed directly by launching the received signal into an injection-locked semiconductor laser. The locked laser conversts phase modulation into current modulation, which is sent to the data detection system after some signal processing. The signal to noise ratio of the receiver can reach 4599O 2 for a 100Mbit/s rate and a 100Khz emitter linewidth, where O is the phase deviation of the modulator

A novel switched-capacitor oscillator based on the n-path filter approach

Abstract: A method of realizing switched capacitor sinusoidal oscillators with a very stable frequency of operation is presented. The oscillating frequency is dependent only on the external clock frequency. The method is arrived at through the n-path filtering principle. Experimental results show the excellent stability and tunability properties of the oscillator. >

Injection locking of a long-pulse relativistic magnetron

Abstract: The authors report the injection locking results of a long-pulse (200-400 ns) high power (20-30 MW) relativistic magnetron at 3.3 GHz. Phase-locking with reproducible locked angle was achieved with an injection power ratio as low as 1:200. The locked states were phase stable to within +or-30 degrees during the pulse. Phase locking physics was studied and important effects due to frequency pushing were identified. The locking bandwidth and the dependence of the final locked phase on injection parameters were measured and found to agree well with theory. >

Injection chaining of diode-pumped single-frequency ring lasers for free-space communication

Abstract: A high-power three-stage laser suitable for use in a space communication system has been built. This laser uses three diode-pumped Nd:YAG oscillators coherently combined using the technique of injection chaining. All three oscillators are in one compact and permanently aligned package, and are actively frequency locked to provide CW single frequency output. The three stages provide the redundancy desirable for space communications.

Fiber-optic sensor using an injection-locked local laser

Abstract: An interferometric fiber-optic sensor using a local laser is proposed. An Er-doped-fiber ring-laser is injection locked to a signal carrier using a fiber coupler, and the extracted carrier is directly homodyned with the signal light at the output of the coupler. With a feedback loop suppressing the local laser instability, demodulation linearity over two decades and minimum detection in the 10/sup -3/ rad range are attained. The Er-doped fiber ring laser constructed for this work has a linewidth of less than 1.4 kHz. Acceptable signal frequency ranges and the linearity and sensitivity of the proposed sensor are examined. Also discussed is the applicability of this configuration to simple, long-spanned sensors. >

Comparison of relativistic magnetron oscillator models for phase-locking studies

Abstract: Four magnetron oscillator models are constructed and analyzed for the study of relativistic magnetron phase locking physics: the extended spoke model, the magnetron-specific equivalent model, the van der Pol equation, and the magnetron oscillator equation. The spoke model reproduces the magnetron specific conductance and susceptance features that are incorporated into other models. The equivalent circuit model and the magnetron oscillator equation model generate the same set of predictions concerning phase-locking condition, locking time, saturation amplitude and final phase. Both models predict a wider locking bandwidth and a shorter locking time as results of the frequency pushing effect. The van der Pol model solved in the fast time scale reveals the dependence of locking time on injection power and oscillator growth rate as well as on injection frequency.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Experiments on fundamental and (sub)harmonic direct optical injection-locking of GaAs FET oscillators

Abstract: Synchronization effects occurring in optically driven GaAs FET oscillators are investigated. In particular, experiments on MESFET RF oscillators phase-locked by means of an amplitude-modulated optical beam illuminating the active device channel are reported. It is shown that, in addition to the fundamental-frequency mode of operation already reported in the literature, harmonic and subharmonic frequency entrainment is also achievable by this technique, confirming theoretical expectations stemming from the electrical injection-locking analogy. >

Voltage-frequency update for nonlinear analysis of free-running and injection-locked multiple device oscillators

Abstract: The standard voltage update algorithm is modified for use in oscillator problems in which the frequency may be unknown and the embedding circuit is a high-impedance resonant circuit. The method is applied to the large-signal steady-state analysis of strongly coupled power-combining oscillator circuits under free-running and externally injection-locked conditions. Information can be obtained about the relative effects of device tuning versus periodicity of the circuit, power variation with tuning, power distribution among the devices, self-locking characteristics, and injection-locking characteristics. >