Showing papers on "Injection locking published in 1986"
TL;DR: In this article, an approach to synchronizing the phases of several oscillators for coherent power combining either in a conventional power-combining circuit or in free space as each oscillator drives an antenna element in a phased array is presented.
Abstract: This paper presents a novel approach to synchronizing the phases of several oscillators for coherent power combining either in a conventional power-combining circuit or in free space as each oscillator drives an antenna element in a phased array. A set of nonlinear differential equations is derived to predict the system's behavior. These equations are used in the computer-aided design and construction of a demonstration three-oscillator inter-injection-locked system at VHF. Good qualitative agreement between initial experimental results and theoretical predictions is observed, and applications of the inter-injection-locking concept to systems are discussed.
178 citations
TL;DR: In this paper, the power spectral densities of single-mode semiconductor laser operating in a regime of injection locking are derived by appropriately taking into account the spontaneous emission processes into the lasing modes of both the master and slave lasers.
Abstract: Analytical expressions for the power spectral densities of intensity and frequency noise of single-mode semiconductor lasers operating in a regime of injection locking are derived by appropriately taking into account the spontaneous emission processes into the lasing modes of both the master and slave lasers. They show how the noise spectra of the slave are influenced by the value of the injected power, by the difference between the emission frequencies of the master and slave optical cavities, and how they are correlated to the noise properties of both the master and the free-running slave. In particular, the very low frequency part of the frequency noise of the slave turns out to coincide with that of the master within a certain frequency region whose range increases as the values of the injected signal does, too. We also present measurements of the power spectral densities obtained by means of an experimental apparatus similar to that described in [1] and show how the experimental results are accounted for by the present theory.
90 citations
TL;DR: In this article, the authors present results of indirect optical injection locking of a free-running 38 GHz (Ka-band) IMPATT oscillator over the Iocking range of 2-132 MHz, depending on the injected power level (amplifier gain).
Abstract: Large aperture phased-array antennas operating at millimeter-wave frequencies are designed for space-based communications and imaging. Array elements are composed of active transmit-receive (T/R) modules that are phase and frequency synchronized to a reference signal at the central processing unit by a fiber-optic (FO) distribution network. The implementation of FO links, synchronizing the millimeter-wave Iocal oscillators (LO's), imposes a great challenge. This paper presents results of indirect optical injection locking of a free-running 38-GHz (Ka-band) IMPATT oscillator over the Iocking range of 2-132 MHz, depending on the injected power level (amplifier gain). In the experiment, the nonlinearity of both the laser diode and the IMPATT oscillator is exploited to achieve 12th subharmonic injection locking. The overall system FM noise degradation of the reference signal is 16 dB at 500-Hz offset. The FM noise degradation is dominated by the theoretical limit of 20 log N, where N is the frequency multiplication factor used in subharmonic injection locking. Methods by which optical injection locking may be extended into 60 and 90 GHz are demonstrated.
69 citations
TL;DR: In this article, a theoretical analysis of the forward and reflected amplitudes in a diode laser oscillator cavity for both a single resonant mode and an injected signal is presented, including gain saturation and allowing the gain coefficient at the injected frequency to be different from that at the resonant frequency.
Abstract: We present a theoretical analysis of the forward and reflected amplitudes in a diode laser oscillator cavity for both a single resonant mode and an injected signal. The analysis includes gain saturation and allows the gain coefficient at the injected frequency to be different from that at the resonant frequency. Analytic solutions for the axially dependent amplitudes are presented for the case of equal gain coefficients. For the more general case, a formula is presented for the intensity necessary for locking, which is shown to reduce in various limits to other expressions previously published. One immediate consequence of the present formalism is that the use of antireflection coatings on the diode end facets should act to reduce the injected signal intensity necessary for locking. In fact, reduction of the reflectivities to values of a few percent should enable locking over the entire gain curve with incident intensities which are small compared to the slave oscillator's normal output.
47 citations
TL;DR: The first self-consistent numerical model to the authors' knowledge of the injection-locking process in a gain-guided diode-laser array reproduces two essential features of device behavior seen in recent experiments: the single-lobed far-field output beam that results from injecting a single end-element of the array and the linear dependence of the far- field beam angle on injection frequency.
Abstract: We report the first self-consistent numerical model to our knowledge of the injection-locking process in a gain-guided diode-laser array. This model reproduces two essential features of device behavior seen in recent experiments: (1) the single-lobed far-field output beam that results from injecting a single end-element of the array and (2) the linear dependence of the far-field beam angle on injection frequency. This angular scanning of the far-field beam angle can be understood on the basis of a simple plane-wave picture in which a change in the injection frequency leads to a tilt of the wave front in the diode-laser array in order to maintain the Fabry–Perot resonance condition.
43 citations
TL;DR: In this article, an S-band master source is used to synchronize two X-band FET oscillators simultaneously, with an 18-MHz locking range using the fiber-optic link nonlinearity.
Abstract: Experimental results of indirect optical injection-locking of two X-band FET oscillators are presented. An S-band master source is used to synchronize both oscillators simultaneously, with 18-MHz locking range using the fiber-optic link nonlinearity. The source of the optical link nonlinearity is traced to the laser diode by interferometric measurement. Both the laser diode and the FET oscillator nonlinearities can be exploited to achieve frequency multiplication of the master oscillator signal. The merits of these different methods are evaluated based on the locking range and the FM noise level of the injection-locked oscillator.
41 citations
TL;DR: A new method of microwave oscillator phase locking is accomplished by modulation of the electron beam before it reaches the cavity oscillator, which provides the coherence required of rf sources for linear accelerators and may enhance gyrotron performance for fusion heating.
Abstract: A new method of microwave oscillator phase locking, exploiting the extended nature of the gyroklystron configuration, is accomplished by modulation of the electron beam before it reaches the cavity oscillator. The amount of power required to give phase locking in a gyrotron is decreased by more than an order of magnitude from that predicted by Adler's theory. In addition, oscillator priming is observed at drive powers far below all other systems tested to date. These new methods provide the coherence required of rf sources for linear accelerators and may enhance gyrotron performance for fusion heating.
32 citations
ENEA1
TL;DR: In this article, the SFUR principle was applied to a TEA CO 2 laser in which the beam is extracted from the confocal point, which results in low divergence and TEM 00 mode.
31 citations
TL;DR: In this paper, the fine structure of the intensity spectrum has been investigated and has revealed a strong modification of relaxation oscillation damping when locking is achieved, which is consistent with theoretical predictions for the locking bandwidth.
Abstract: Detailed observations of an injection-locked semiconductor laser have allowed a verification of theoretical predictions for the locking bandwidth. In parallel, the fine structure of the intensity spectrum has been investigated and has revealed a strong modification of relaxation oscillation damping when locking is achieved.
30 citations
TL;DR: In this paper, indirect optical injection-locking of two X-band oscillators was used to lock both oscillators over 18 MHz using the laser diode nonlinearities, and the system FM noise degradation was 14 dB and the means to improve system performance were suggested.
Abstract: Experimental results of indirect optical injection-locking of two X-band oscillators are presented. An S-band master source is used to lock both oscillators over 18 MHz using the laser diode nonlinearities. System FM noise degradation is 14 dB and the means to improve system performance are suggested.
27 citations
01 Oct 1986
TL;DR: In this article, the experimental results of a fiber-optic distribution network at millimeter wave frequency of 38GHz (Ka-band) are presented, and the results of 500MHz-1GHz FO link characteristics such as frequency response flatness, harmonics, and third order intermodulation distortion are presented.
Abstract: Large aperture phased array antennas are designed with fiber-optic distribution networks to provide phase and frequency reference signals, control signals for beam steering and shaping, and data/frequency hopping signals to MMIC active T/R modules. The experimental results of a FO communication network at millimeter wave frequency of 38GHz (Ka-band) are presented. The results of 500MHz-1GHz FO link characteristics such as frequency response flatness, harmonics, and the third order intermodulation distortion are presented. Results of stabilization of a 38GHz IMPATT oscillator using indirect optical injection locking is also discussed. A locking range of 132MHz using 45dB amplification gain is demonstrated. The overall system FM noise degradation is measured to be 16dB. The communication link is established by up-conversion of the data link with the stabilized LO. Results of a true time delay phase shifter using a novel fiber striching technique is presented. A phase shift as high as 20° at 10GHz is achieved using the expansion properties of a piezo-electric ring by applying dc voltage.
TL;DR: In this paper, a single far-field lobe and singlemode operation of a 20-element GaAlAs gain-guided coupledstripe array with 315 mW of output was obtained by injection locking with 3.9 mW incident power.
Abstract: Single far-field lobe and single-mode operation of a 20-element GaAlAs gain-guided coupled-stripe array with 315 mW of output was obtained by injection locking with 3.9 mW of incident power. The 0.31° lobe width was near the diffraction limit. An external small-signal gain of 19 dB was obtained.
TL;DR: A new Nd:YAG-pumped picosecond optical parametric oscillator that generates bandwidth-limited pulses using two LiNbO3 crystals and the spectral intensity of a quantum noise at λ = 0.85 μm is measured.
Abstract: We report a new Nd:YAG-pumped picosecond optical parametric oscillator that generates bandwidth-limited pulses. Using two LiNbO3 crystals, it produces tunable, near-1.4-μm (signal-wave) pulses of 18-psec duration and Δν = 1.2 cm−1 FWHM (Δντ = 0.7). The output energy of the optical parametric oscillator in a signal wave is no less than 2 mJ with 10% energy stability. The key to this device is the injection of cw single-frequency GaAs diode-laser radiation. Using the injection of diode-laser radiation, we have measured the spectral intensity of a quantum noise at λ = 0.85 μm. The intensity was found to be 6 ± 2 W/cm2 cm−1 sr (theoretical value, 4.7 W/cm2 cm−1 sr).
Patent•
07 Oct 1986
TL;DR: By optically injecting a single end-element of a semiconductor laser array, both the spatial and spectral emission characteristics of the entire laser array is controlled as discussed by the authors, with the output of the array locked.
Abstract: By optically injecting a single end-element of a semiconductor laser array, both the spatial and spectral emission characteristics of the entire laser array is controlled. With the output of the array locked, the far-field emission angle of the array is continuously scanned over several degrees by varying the injection frequency.
02 Jun 1986
TL;DR: In this paper, the authors presented results of indirect optical injection locking of a free-running 38GHz (Ka-band) IMPATT oscillator over the locking range of 2 to 132MHz, depending on the injected power level (amplifier gain).
Abstract: This paper presents results of indirect optical injection locking of a free-running 38GHz (Ka-band) IMPATT oscillator over the locking range of 2 to 132MHz, depending on the injected power level (amplifier gain). In this experiment, The nonlinearity of the both laser diode and the IMPATT, are exploited to achieve twelfth sub-harmonic injection locking. Methods by which optical links may be extended into 60 and 90GHz are demonstrated.
01 Oct 1986
TL;DR: In this article, a method for the analysis of driven oscillators under high-level injection is presented, which applies to single-loop feedback systems with a memoryless nonlinear element and a second-order (high-Q) tank circuit.
Abstract: A method for the analysis of driven oscillators under high-level injection is presented. It applies to single-loop feedback systems with a memoryless nonlinear element and a second-order (high-Q) tank circuit. The analysis technique employed combines the classical block-diagram approach with an improved firstharmonic dynamic modelling to provide a couple of differential equations capable of accounting for the amplitude-dependence effects arising under large-signal operation. On this basis, first-and second-order approximate expressions are also derived, which allow a better understanding of the validity limits of previous theories on this subject. As an example of application, both the steady-state and transient behaviour of synchronised hyperbolic-nonlinearity oscillators is investigated.
TL;DR: In this paper, the effects of an injected laser field on an index-guided semiconductor laser array were analyzed and it was shown that a sufficiently intense injected field can cause the array to operate predominantly in the lowest order mode.
Abstract: This paper describes an analysis of the effects of an injected laser field on an index-guided semiconductor laser array. We assume an injected field that is resonant with the lowest order array mode and a free-running array that is either operating with a higher order array mode or is not frequency locked. For both cases, a sufficiently intense injected field is found to cause the array to operate predominantly in the lowest order mode. Also, according to our analysis, for certain array configurations, it is more advantageous to have the injected field present during the startup of oscillation than to introduce it after the free-running array has reached steady state. Finally, the injection-locked array is found to contain a tilt in the output beam.
01 Mar 1986
TL;DR: A Synchronous Oscillator tracks, filters, divides, and amplifies the input carrier in a single process to achieve narrow-resolution bandwidth, high input-signal sensitivity, and fast acquisition.
Abstract: A Synchronous Oscillator (SO) tracks, filters, divides, and amplifies the input carrier in a single process. Narrow-resolution bandwidth, high input-signal sensitivity, and fast acquisition are the most important properties of the SO, while the resolution bandwidth remains as its most unique functional behavior.
02 Jun 1986
TL;DR: In this paper, the effects of multimode fiber-optic coupling on optical injection-locked GaAs MESFET oscillators are discussed and the effect of laser mode locking and fiber modal microphone discussed.
Abstract: We discuss the effects of multimode fiber-optic coupling on optical injection-locked GaAs MESFET oscillators. Locking frequency range data are presented and the effects of laser mode locking and fiber modal microphone discussed. The effects of FET photodetection efficiency as a function of modulation frequency are identified together with means for locking range enhancement.
TL;DR: In this article, a single-mode operation of a cw ring dye laser has been obtained by injection of cw singlemode radiation, and the intracavity power of this system was used to generate tunable singlemode uv radiation by frequency doubling in a temperature phase-matched ADA crystal.
Abstract: High-power single-mode operation of a cw ring dye laser has been obtained by injection of cw single-mode radiation. The intracavity power of this system was used to generate tunable single-mode uv radiation by frequency doubling in a temperature phase-matched ADA crystal: up to 45 W intracavity fundamental power and up to 70 mW extracted uv power have been observed. A theoretical treatment of the injection locked cw ring dye laser system is given for the stationary state. Expressions for the intracavity intensities as a function of the small-signal gain and the saturation intensity are derived.
TL;DR: In this article, a ten-element gain-guided coupled stripe array using a new technique based on injection locking was used to measure time-dependent changes in the cavity resonance frequency.
Abstract: Time-dependent changes in the cavity resonance frequency were measured in a ten-element gain-guided coupled stripe array using a new technique based on injection locking. Sensitivity of the frequency to changes in the array current was 0.7 GHz/mA at dc and 0.04 GHz/mA for 1.0 MHz sine-wave modulation. The current-to-frequency modulation transfer function for the array was determined, and it was concluded that the transition from thermal to carrier-induced frequency modulation occurs in the region between 105and 106Hz.
01 Jan 1986
TL;DR: In this paper, a low-loss SAW comb filter was proposed, where the insertion losses at comb peaks ranged from 3.7 dB to 9.6 dB over the total comb response with group delays 3 < 1 ps.
Abstract: Coupling-of-modes (COM) theory is used in the analysis and design of a SAW single-phase unidirectional transducer (SPUDT) in a low-loss SAW comb filter. Comb separations are given by 1/T, where T = time delay between IDT's within each SPUDT. Devices on lithium niobate yielded insertion losses at comb peaks ranging from 3.7 dB to 9.6 dB over the total comb response with group delays 3 < 1 ps, in excellent agreement with theory. h multifrequency delay line oscillator was obtained using such a comb filter in the feedback loop. With pulsed injection-locking, frequency hopping times of 1-2 ps were realized; as illustrated for a 60-100 MHz SAW oscillator with 0 dBm power level and 10 MHz between individually selectable oscillator frequencies.
TL;DR: In this article, a linear theory was proposed to explain the experimentally observed emission angle scanning of an injection-locked diode laser array when the frequency of the injected light is changed, based on eigenmode analysis of the coupled waveguides and on the use of the antenna array theory for the far field pattern.
Abstract: We present a linear theory to explain the experimentally observed emission angle scanning of an injection‐locked diode laser array when the frequency of the injected light is changed. This theory is based on eigenmode analysis of the coupled waveguides and on the use of the antenna array theory for the far‐field pattern. The experimental results are explained in terms of the resonant excitation of eigenmodes, which selects the far‐field pattern associated with the resonant mode. The agreement with published results is good.
Patent•
14 Aug 1986
TL;DR: In this article, a four-diode bridge is positioned within the cavity of a Gunn diode oscillator, and a subharmonic signal is applied to the diode bridge, which couples an odd harmonic of the injected signal into the cavity.
Abstract: A four-diode bridge is positioned within the cavity of a Gunn diode oscillator. A subharmonic signal is applied to the diode bridge and the diode bridge couples an odd harmonic of the injected signal into the cavity. The cavity is thus caused to resonate at the odd harmonic of the injected signal. The injected signal can be changed using a frequency synthesizer in order to provide a microwave oscillator with multiple-channel operation. The diode bridge provides a feedback signal indicative of the phase of cavity oscillation. The feedback signal is applied to a varactor which pretunes the Gunn diode oscillator and thereby provides phase-locked control.
09 Jun 1986
TL;DR: In this article, the angular divergence of a copper laser pulse starts at the aspect angle of the resonator and reduces by the magnification M on each succeeding round trip, and it is not until the third round trip that the beam divergence approaches the diffraction limit.
Abstract: Unstable resonators are typically employed to obtain reasonable beam quality from copper laser oscillators. However, due to relatively long round-trip times in the resonator (~15 ns) relative to the inversion time (~50 ns) only three to four round trips are possible. The angular divergence of a copper laser pulse starts at the aspect angle of the resonator and reduces by the magnification M on each succeeding round trip.1 For our copper lasers this initial full angle divergence is θl ≃ 103 × (2.44λ/D). With an M= 15 unstable resonator it is not until the third round trip that the beam divergence approaches the diffraction limit. Since the gain is dropping by the third round trip in the resonator, the resulting laser pulse has most of its energy in highly diverging components and only a small fraction in the later lower divergence component. Propagation of this beam through a relatively small f/No. optical system causes nearly three-fourths of the pulse energy and two-thirds of the pulse length to be lost from the transmitted beam.
TL;DR: In this paper, the dominant channels of decay are accessible only due to anharmonic terms in the potential energy surface, which are often needed for a realistic description of molecular dynamics, and the dominant channel of decay can only be accessed due to these terms.
Abstract: Anharmonic potential energy surfaces are often needed for a realistic description of molecular dynamics. In some cases the dominant channels of decay are accessible only due to anharmonic terms in the potential energy surface.
02 Jun 1986
TL;DR: In this paper, an array of three microstrip patch antennas, each connected by a matching network to an IMPATT diode, was investigated at 10.23 GHz by feeding only the center element with an injectionlocking signal, which then appeared at the input to the other two elements by free space mutual coupling.
Abstract: An array of three microstrip patch antennas, each connected by a matching network to an IMPATT diode, has been investigated. Coherent radiation from the array was obtained at 10.23 GHz by feeding only the center element with an injectionlocking signal, which then appeared at the input to the other two elements by free space mutual coupling. The three IMPATTs injection locked successfully in this manner. A beamwidth of 38 degrees and sidelobe level of -10 dB were achieved, values consistent with the theory for coherent radiation from an array of this configuration. An RF efficiency of 90% and a bandwidth of 30 MHz were measured.
02 Jun 1986
TL;DR: In this article, the authors present a novel circuit topology which leads to the inter-injection-locking of a set of interconnected oscillators, where each oscillator is coupled only to its two nearest neighbors, the scheme is very well adapted to integrated planar construction.
Abstract: Although the principle of injection locking has been applied to single- and multiple-device oscillators at microwave through millimeter wavelengths, the technique has not found many uses in hybrid or monolithic microwave integrated circuits. We present here a novel circuit topology which leads to the inter-injection-locking of a set of interconnected oscillators. Since each oscillator is coupled only to its two nearest neighbors, the scheme is very well adapted to integrated planar construction. Furthermore, phase control of only one injection power source can control the phases of all oscillators in the system in a manner suitable for driving a phased antenna array. A summary of the theory is followed by a description of results from an experimental VHF three-oscillator system. We conclude with a discussion of some proposed applications of inter-injection-locked systems.
TL;DR: In this paper, experimental observations on the amplitude modulation of a 9.347 GHz Gunn oscillator when it is injection-locked by an FM signal were carried out and the dependence of both the FM-AM conversion efficiency and the harmonic distortion of the detected signal on the system parameters was discussed in detail.
Abstract: This paper describes experimental observations on the amplitude modulation of a 9.347 GHz Gunn oscillator when it is injection-locked by an FM signal. The dependence of both the FM-AM conversion efficiency and the harmonic distortion of the detected signal on the system parameters is discussed in detail. Numerical analysis for the system is also presented. The investigations carried out indicate that an injection-synchronized microwave oscillator can be used as an efficient FM-AM converter so that together with an AM detector, it can serve the purpose of a faithful FM demodulator, expecially for low-index FM signals.