Showing papers on "Injection locking published in 1989"

Additive pulse mode locking

Abstract: A new principle of mode locking is analyzed: additive pulse mode locking. It is shown to be operative in two-cavity soliton lasers, but it also permits mode locking with fibers in the positive dispersion regime. A simple model is developed that displays the pulse-shortening mechanism. Parameter ranges, within which this principle can be exploited, are given. Comparisons with experiments are made.

Injection locking of a 13-W cw Nd:YAG ring laser.

Abstract: A lamp-pumped, 13-W cw Nd:YAG ring laser at 1.064 μm is injection locked using a 40-mW single-frequency diode-laser-pumped Nd:YAG laser as the master oscillator. The phase fidelity of the injected slave to the master is measured using an all-optical technique.

Phase locking of high-power microwave oscillators

Abstract: Phase locking is considered both for a case in which an oscillator is driven by an external signal without feedback, and for a case in which two coupled oscillators drive each other. A comprehensive sustained oscillator model is used for the driven microwave cavity. The new locking conditions for two coupled oscillators show that phase locking can occur only when the connector contributes the zero or π phase delay. Temporal behavior is solved numerically. Calculations with large priming power agree with the experiments on a high‐power magnetron driven vircator in which there is no feedback to the magnetron. The mutual drive calculations also agree with the experiments on high‐power coupled magnetrons.

Optical communication by injection-locking to a signal which modulates an optical carrier

Abstract: An optical communication system is disclosed including an all-optical device whose output modulated optical beam is locked to an input modulated optical beam. In a specific embodiment of the system, the device may be a self-electro-optic effect device (SEED), which is operated as an oscillator by means of an associated tank circuit. Such an embodiment permits recovery of a clock frequency from a bit stream which is input into the device. When the output of the device is directed into an optical decision element, an all-optical regenerator may be realized.

Optical phase control of an optically injection-locked FET microwave oscillator

Abstract: A simple technique is proposed and demonstrated for controlling the phase of an optically-injection-locked 7.2-GHz FET oscillator. The relative phase phi between the oscillator and the locking signal is adjusted by optically tuning the oscillator frequency. Locking characteristics described include locking bandwidth (2.6 MHz), phase tuning range (187 degrees ), phase modulation ( beta =0.69 at 500 kHz), and optical tuning (125 MHz). >

Timing recovery scheme for burst communication systems having a VCO with injection locking circuitry

Abstract: A timing recovery apparatus for a burst mode communication receiver. The apparatus provides for optimum sampling and digitizing of received data at a plurality of data rates. In particular, a VCO is phase-locked to a local frequency reference prior to data being received. A reference timing preamble transmitted prior to the data is filtered and fed to the VCO causing it to injection lock such that the VCO becomes phase aligned with the preamble. The VCO is then permitted to "free run" during data transmission and continues to operate at substantially the same frequency. A synchronous divider and multiplexer, responsive to the VCO, allows selection of sampling clocks for the plurality of data rates. The divider is forced to a known state during VCO injection locking, to assure that the sampling clocks have maintained the proper phase for optimal sampling at the corresponding data rate. Further, means is provided to monitor the frequency of the VCO. Should the VCO frequency drift more than a predetermined amount an indication of such is produced.

Injection-beam parameter optimization of an injection-locked diode-laser array.

Abstract: The dependence of the far-field distribution of an externally injection-locked array on the width and power of the injected beam was determined by numerical simulation. The fraction of total power contained in the diffraction-limited lobe portion of the far field was significantly larger for wide-beam injection (95%) than for single-point injection (70%). Qualitative agreement with experimental results using a 20-element array was observed.

Optical control of frequency and phase of GaAs MESFET oscillator

Abstract: Results are presented for a system combining optical injection locking and closed-loop optical-frequency tuning to achieve accurate phase and frequency control of a MESFET oscillator operating at 1.3 GHz. The system might find application in the phase synchronisation of modules in phasedarray antennas, where the phase reference is distributed by an optical-fibre network.

Methods of passive and active mode locking using intracavity optical frequency mixing.

Abstract: The mode-locking technique based on intracavity second-harmonic generation is extended to sum- and difference-frequency generation. Simultaneous passive mode locking of two different types of laser in a combined cavity is thus possible. By using the same principle, a laser may be actively mode locked by injection of a pulse train from another mode-locked laser.

Energy transfer between injection-locked single-mode diode lasers by two-beam coupling in BaTiO(3).

Abstract: Two-beam coupling in photorefractive BaTiO(3) is used to combine beams coherently from two injection-locked single-mode diode lasers operating at 830 nm. We are able to transfer more than 70% of the power in one beam to the other beam with this method.

Integrated injection-locked high-power cw diode laser arrays

Abstract: We report the first integrated injection‐locked high‐power continuous‐wave diode laser array with an on‐chip independently controlled master laser. This device emits a near‐diffraction‐limited (0.5° full width at half maximum) single‐lobed far‐field emission beam at single‐facet powers up to 125 mW. Also, by current tuning the emission wavelength of the master laser, we observe steering of the single‐lobed emission over an angular range of 0.50° at a rate of −1.2×10−2 deg/mA. Our work demonstrates the feasibility of incorporating active optical injection and control in the structure of high‐power diode laser devices.

Simple way to improve a tunable argon fluoride laser

Abstract: The locking efficiency and stability of a Lambda Physik EMG150 tunable ArF laser was significantly improved in a simple way. The active gain volume of the oscillator laser was increased by a factor of 5 by replacing the 1‐mm circular holes supplied with the original laser by 1 mm×5 mm rectangular apertures. The resulting rectangular output of the oscillator was condensed with a cylindrical telescope and used for injection locking. The scanning range, locking efficiency, and stability of the laser were significantly improved.

Low power timekeeping

Abstract: Low-power timekeeping methods have been developed that provide improved accuracy over the full military temperature range. These methods provide tradeoffs of accuracy vs. power consumption dependent upon the application. The system achieves this performance by using a microcomputer-compensated crystal oscillator (MCXO) to periodically update a low-power oscillator clock system. This technique does not substantially increase the power dissipation because the MCSO is turned on for only a few seconds each time to recalibrate the clock oscillator frequency. Using this technique, a clock oscillator of +or-5*10/sup -6/ over the temperature range can be made to approach the +or-*10/sup -8/ accuracy of the MCXO. >

Operation and theory of a driven single-mode electron cyclotron maser.

Abstract: A study is made of the operation of the electron cyclotron resonance maser (ECRM), when subjected to an external rf signal. The signal is introduced both via direct injection through a coupling hole in the oscillator and by modulating the electron beam in separate cavities, upstream of the oscillator. Experiments using both one and two ``prebunching'' cavities are reported. It is experimentally found that the gyromonotron, a specific embodiment of the ECRM, can be phase locked by premodulating the electron beam at drive power levels more than two orders of magnitude below that predicted by Adler's widely applicable theory for single-cavity oscillators. A perturbation theory is used to predict the phase-locking frequency band for a gyromonotron with any number of prebunching cavities. The predictions of this theory agree with the experimental results for two- and three-cavity phase locking. An investigation is made into the general amplitude and frequency response of the ECRM to an applied external signal. Experimentally, three distinct regions of qualitatively different ECRM behavior are noted: soft excitation, which is free, self-excited oscillation; hard excitation, where the oscillation requires an external impulse for startup; and amplifier, in which the output power level and frequency are linearly related to the drive in the small-signal regime.

Clock signal generator having back-up oscillator substitution

Abstract: A clock signal generator comprising a first oscillator which normally supplies clock pulses to the output of the clock signal generator, a first counter for counting the pulses generated from the first oscillator and producing a carry signal after counting n1 pulses generated from the first oscillator, a second oscillator for producing clock pulses for possible back-up purpose, a second counter for counting the pulses generated from the second oscillator and adapted to produce a carry signal after counting n2 pulses generated from the second oscillator and to be reset by the carry signal from the first counter, n2 being larger than n1, and a control circuit which blocks the output from the second oscillator as long as no carry signal is supplied thereto from the second oscillator. Therefore, should the first oscillator fail to produce period pulses, the second counter is not reset any more and the control circuit stops blocking the pulses from the second oscillator and forwards them to the output of the clock signal generator. Thus, the clock signal generator can continue to supply clock pulses even when one of its oscillators should fail to operate properly, and the reliability of the clock signal generator is improved.

Coherent operation of injection‐locked monolithic surface‐emitting diode laser arrays

Abstract: A row of six surface‐emitting GaAlAs laser diode arrays was locked in a coupled resonator configuration by means of interconnecting waveguides. An external master oscillator was injected into the first array in order to achieve single longitudinal mode operation and wavelength tunability. Spectral data show all six devices were locked in a single longitudinal mode, with tunable operation of over 60 A. Far‐field fringe visibilities greater than 60% were achieved at 100 mW output powers.

Side-mode injection locking of semiconductor lasers

Abstract: Longitudinal mode selection in diode lasers by injection locking has been studied using the standard multimode rate equations with an optical injection term, and with the effects of spontaneous emission included. The phenomena of spectral narrowing and power switching between the dominant free-running mode and the injected target mode are illustrated and discussed. In general, injection locking into the long-wavelength side of the spectrum is more effective than into the short-wavelength side because of the gain peak shift. The relaxation oscillation frequency is estimated using a small-signal analysis of the single-mode rate equations, an approach that is valid provided the external injection is strong enough. Our calculations indicate that around the gain peak the relaxation oscillation frequency strongly depends on the wavelength of the injected target mode, because of the changing differential gain. Modes with shorter wavelengths have faster relaxation oscillations due to larger differential gain. This can be helpful in increasing the transmission speed in optical communication applications.

Phase lock clock recovery with aided frequency aquisition

Abstract: In a burst mode fiber-optic transmitter-receiver or bus interface unit (BIU), the clock recovery process by a phase lock loop (PLL), or more generally a servo loop, detects the frequency difference between the PLL oscillator and the transmitter oscillator, and generates a control voltage which is combined with the voltage controlled oscillator (VCO) error voltage to urge the PLL oscillator towards the transmitter's frequency. An activity detector detects the presence of received signal, and "freezes" or holds the control voltage to the PLL so the PLL is free to slew to the frequency and phase of the clock of the received burst. Thus, the PLL is maintained near the expected frequency of the received clock signal for fast acquisition. After the burst, the activity detector once again allows the frequency control signal to assert command of the VCO frequency.

Comment on ``Squeezing and frequency jump of a harmonic oscillator''

Abstract: The relevance of the conclusions of a paper by Fan and Zaidi [Phys. Rev. A 37, 2985 (1988)] concerning the possibility of generating squeezed states of a harmonic oscillator by sudden change of its frequency is analyzed.

A feedback model of millimeter wave harmonic oscillators and its application

Abstract: In this paper a feedback model of second harmonic oscillators is developed. By using describing functions of nonlinearity of active devices, the performances of second harmonic oscillators are studied. Frequency dependence of I–V characteristics of active element are taken into account. The ratio of maximum output power of second harmonic to fundamental is given. The maximum harmonic locking bandwidth of injected harmonic oscillator is derived. The theoretical prediction is compared with experimental results.

Oscillators and amplifiers in integrated E-plane technique

Abstract: An overview is presented of solid-state oscillators and amplifiers realized in E-plane technology. The circuit topology, basic design procedures, and performance characteristics are described and compared. Gunn oscillators, IMPATT oscillators, transistor oscillators, injection-locked Gunn oscillators, and transistor amplifiers are surveyed. Gunn and transistor oscillators have been realized successfully for frequencies from 10 to 110 GHz, thus covering almost the entire frequency range suitable for E-plane technology. IMPATT oscillators are difficult to design and to reproduce in quasi-planar form because of the high impedance ratio that must be overcome by the circuit. E-plane FET amplifiers have been built for frequencies up to 60 GHz. >

A MMIC based injection locked oscillator for optically fed phased array antennas

Abstract: 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 sub-assemblies of optically fed phased array antennas. The circuit utilizes two FETs and a dielectric resonator, which serves as a frequency-dependent feedback element. The circuit provides significant amplitude and phase noise suppression and is designed to operate around 10 GHz. The circuit realization is fully compatible with MMIC (monolithic microwave integrated circuit) technology. >

The effects of ground‐state dynamics on the emission spectra of electric‐discharge‐pumped XeCl lasers: A model for injection locking

Abstract: The bandwidth of excimer lasers is typically 1–10 A as a result of their transitions being multiline or bound‐free. To obtain high power with narrow bandwidth injection locking is usually required. In this paper, we investigate the spectral characteristics of electric‐discharge‐pumped XeCl (B→X) lasers during injection locking and free‐running operation. This study is performed using results from an electron kinetics and plasma chemistry model for Ne/Xe/HCl/H2 mixtures which includes multiline laser extraction. We find that the experimentally observed lasing spectrum cannot be explained if a thermal distribution is used for the vibrational levels of the X state. Therefore, the vibrational levels of the B, C, and X states are explicitly included in the model and the gain spectrum is computed using Franck–Condon factors. Results from the model indicate that bottlenecking occurs on the v’=0→v‘=1 transition, while the dissociation rate for XeCl(X,v‘=2) is faster than the removal rate for XeCl(X,v‘=1). Injection locking characteristics are examined as a function of injection intensity and small‐signal gain. Due to nonequilibrium dynamics in the ground state, locking efficiency does not necessarily increase with increasing small‐signal gain.

FM demodulator including injection locked oscillator/divider

Abstract: An FM demodulator comprises an injection locked oscillator/divider for receiving an input signal to be demodulated. The injection locked oscillator/divider is coupled via a divider to a frequency discriminator, such as a quadrature demodulator, for providing a demodulated output signal. A feedback loop is provided to afford the demodulated output signal to a varactor tuning circuit of the injection locked oscillator/divider so that the center frequency of the injection locked oscillator/divider is constrained to correspond with the frequency of the input signal. The FM demodulator provides improved threshold extension and demodulated video bandwidth.

Coherent optical communication with injection-locked high-power semiconductor laser array

Abstract: Heterodyne FSK communication at 110Mbit/s is demonstrated with an injection-locked high-power 20-stripe semiconductor laser array. We show that a high-power (>300mW) coherent optical transmitter can be constructed without penalty in bit error rate performance.

Proposed injection locking of a long-pulse relativistic magnetron

Abstract: We report results of the initial operation of a 1µs rel-ativistic magnetron system to be used in the phase lockingexperiment. Full voltage pulse length with no evidence ofdiode shorting due to plasma closure is achieved in smoothbore geometry. The operating characteristics of the 700 kV, 700 A modulator together with the computerized con-trol /acquisition system for the phase locking experiment isalso described.2. INTRODUCTION Phase locking of nonlinear oscillators is a classical ex-ample of a good old topic in physics, and has been studiedextensively over the last 40 years. A surprisingly wide rangeof natural phenomena and an even wider range of applicationsin daily life can be described by the phase locking model:from synchronization of clocks, to stellar pulsation, to radiowave reception, to pace makers in the heart, to diode laser array. In many applications involving large numbers of highpower microwave oscillators, it is desirable to synchronizethe frequency and phase of each individual oscillator relativeto some stable external reference. It is especially true whena high energy density or the pulse -to -pulse phase coherenceis required, as in the case of high field -gradient accelerators.One way of achieving phase control is by injecting powerfrom a low power reference source directly into the oscillatorsto be locked. Relativistic magnetrons1'2 have demonstratedhigh power (multi gigawatt) with high efficiency (more than30 %) started in the late 70's. Successful injection locking ofthese high power oscillators will yield even higher power den-sity and field gradient. This scenario, however, has not beenrealized yet. In this paper, we will describe an experiment'set up for phase locking a relativistic magnetron using exter-nal low power injection. Reciprocal locking of oscillators isanother possible method for achieving high power densities.

Radar system employing injection locked transmitter stage

Abstract: A radar transmitter chain employing injection locked oscillator, e.g., a magnetron, as an output stage. Problems arise with maintaining the injection locking bandwidth centered on the radar source transmit frequency. This alignment is maintained by allowing the magnetron (38) free running frequency to drift, along with its injection locking bandwidth and then to force the radar source frequency (30) to follow the magnetron frequency. A phase difference measurement (44) between the injection signal (35) and the magnetron output signal (37) provides the control for a feedback loop (60) which may control a tunable VCO (48) or selection from a bank of fixed frequency oscillators (78).

Phase locking laser diodes using photorefractive coupling

Abstract: Several authors have reported strong frequency pulling while coupling laser diodes using phase conjugation. However, to our knowledge, no one has proven stable phase locking by interfering the laser outputs to show stable fringes. A stable phase lock has been obtained, and the geometry used is compared with those proposed previously.

Very narrow-bandwidth tunable infrared difference frequency generation with injection-locked dye lasers

Abstract: Two flashlamp pumped dye lasers of very high spectral quality are mixed in a LiIO3 crystal to generate a tunable infrared beam through the difference frequency mixing. Thanks to the injection-locking process of the pulsed dye lasers leading to a linewidth of 6 MHz with peak powers of about 10 kW, we obtain an IR beam tunable from 3.5 to 5.9 μm with a peak power of 40 W and a linewidth of 9 MHz. As an application we present a spectrum of N2O obtained by differential absorption near 1880 cm−1. The lines of thisQ-branch are Doppler limited at the working pressure (102 Pa).