Showing papers on "Parametric oscillator published in 1970"

Quantum-Mechanical Amplification and Frequency Conversion with a Trilinear Hamiltonian

Abstract: A description of the parametric amplifier and frequency converter is presented without introducing the classical (i.e., parametric) approximation for the pumping field. Constants of the motion are found which reduce the solution of the Schr\"odinger equation to the diagonalization of a matrix. This diagonalization is accomplished numerically, and the eigenvalues and eigen-functions of a system with fixed energy are calculated. The time-dependent behavior of the mean number of photons in the amplified or frequency up-converted field is presented. The time evolution of the probability distributions is illustrated. The technique is extended to the problem of coherent spontaneous emission from a system of $N$ two-level atoms interacting with the radiation field where both the atomic system and the radiation field are quantized.

On cross-waves

Abstract: Cross-waves are standing waves with crests at right angles to a wave-maker. They generally have half the frequency of the wave-maker and reach a steady state at some finite amplitude. A second-order theory of the modes of oscillation of water in a tank with a free surface and wave-makers at each end leads to a form of Mathieu's equation for the amplitude of the cross-waves, which are thus an example of parametric resonance and may be excited at half the wave-maker frequency if this is within a narrow band. The excitation depends on the amplitude of the wave-maker at the surface and the integral over depth of its amplitude. Cross-waves may be excited even if the mean free surface is stationary. The effects of finite amplitude are that the cross-waves approach a steady state such that a given amplitude is achieved at a frequency greater than that for free waves by an amount proportional to the amplitude of the wave-maker. The theory agrees reasonably well with the experimental results of Lin & Howard (1960). The amplification of the cross-waves may be understood in terms of the rate of working of the wave-maker against transverse stresses associated with the cross-waves, one located at the surface and the other equal to Miche's (1944) depth-independent second-order pressure. The theory applies to the situation where the primary motion consists of standing waves and the cross-waves are constant in amplitude away from the wave-maker, but certain generalizations may be made to the situation where the primary waves are progressive and the cross-waves decay away from the wave-maker.

Efficient internal optical parametric oscillation

Abstract: Efficient internal optical parametric oscillation has been obtained using a LiNbO3 crystal inside the resonator of a continuously pumped repetitively Q‐switched 1.06μ Nd:YAG laser. Dielectric mirrors are coated directly on the plane‐parallel end faces of the crystal, and no focusing optics are used inside the laser. The oscillator operates near degenerate with outputs near 2μ. Average output powers as high as 350 mW and 75 % depletion of the available pump power are observed. This represents an order of magnitude larger output power than previously reported for a parametric oscillator. Internal oscillation causes stretching of the laser pulses to as much as five times the normal length, with corresponding increases in oscillator pulse length. Operation of this internal oscillator is compared to that of a similar external oscillator pumped by the same laser.

Optical parametric oscillation in proustite

Abstract: The nonlinear material proustite (Ag3 AsS3) has been employed in an optical parametric oscillator. The oscillator is pumped by the 1.06‐μ output from a repetitively Q‐switched Nd : YAG laser and has signal and idler outputs near 2.1μ. Operation of the oscillator is described and the results of optical parametric fluorescence experiments are given. The primary limitation on the operation of the oscillator is surface damage to the proustite crystal.

Spatially uniform and alterable shg phase‐matching temperatures in lithium niobate

Abstract: By the addition of MgO to a congruent melt, one can obtain x‐axis crystals of lithium niobate several centimeters in length, whose phase‐matching temperature for second harmonic generation (SHG) has been increased appreciably while the spatial uniformity of Tpm has been preserved Thus it is possible to operate a 05145‐μ pumped parametric oscillator in a convenient wavelength regime and at a temperature above that for damage annealing

Optical parametric oscillation in lithium iodate

Abstract: Optical parametric oscillation has been achieved in LiIO3 pumped by a pulsed ruby laser, with tunable output to 4μ. Operation of the singly resonant oscillator is described and threshold measurements are compared with theory.

Tunable Parametric Oscillator Using a Guided Wave Structure

Abstract: A proposed tunable optical parametric oscillator in a guided wave structure consisting of a thin nonlinear slab asymmetrically sandwiched by two linear dielectrics is treated theoretically. The two linear dielectrics have smaller indices of refraction than the nonlinear dielectric, and the oscillator frequency is tunable by changing the refractive index of one of the linear dielectrics. For a GaAs nonlinear film sandwiched by Irtran 3 or Sapphire and liquid, calculations show that the oscillation frequency can be tuned over ±35% of the subharmonic frequency of a 1.06µ pump as the refractive index of the liquid is varied from 1.25 to 1.6. For reasonable parameters, the threshold power is estimated to be 7 milliwatts. The phase matching conditions and oscillation characteristics for parametric interaction in a guided wave structure are derived and discussed.

Experimental Observation of and Comments on Optical Parametric Oscillation Internal to the Laser Cavity

Abstract: The theory of an optical parametric oscillator located internal to the cavity of the pump laser has recently been presented by Oshman and Harris. An oscillator of this type has been constructed and the details of its operation are presented here. Several features predicted by the theory have been observed; in particular a form of relaxation oscillation peculiar to the internal oscillator has been observed for the first time. In addition to the experimental results the question of the stability of the various modes of operation and factors affecting the pulse repetition rate of the pulsing solution are considered.

Passive pulse transmission mode operation in a q-switched laser having an internal parametric oscillator

Abstract: Passive pulse transmission mode (PTM) operation is established in a Q-switched laser by means of a parametric oscillator located within the resonator of the laser which functions as a pump for the oscillator. The oscillator is adapted to deplete the pump at the moment the incavity pump power reaches a maximum, resulting in highly efficient conversion of pump power to signal and idler power. In one embodiment, one of the laser reflectors is made highly transmissive to the nonresonant signal radiation, and the oscillator is made singly resonant (SRO) at the idler frequency, resulting in a substantial fraction (ideally at least one-half) of the laser power being coupled out of the cavity in twice the round trip time of the laser resonator, but at the signal wavelength. Since the SRO is tunable, the short, high power output pulse is also tunable from the pump wavelength to longer wavelengths. Other embodiments utilizing doubly resonant oscillators and ring-type configurations are also disclosed.

Generation of Fractional Harmonics in a Resonant Ultrasonic Wave System

Abstract: The problem of a fluid‐filled cavity caused to resonate by an ultrasonic wave is described as a parametric phenomenon. Variation of the cavity resonance frequency as a result of the periodic change of length produces the condition for parametric resonance. As a result, fractional harmonics of the driver transducer frequency are generated. The wave equation describing the system is transformed into an ordinary differential equation with periodic coefficients. The solution of this differential equation (Mathieu's equation) predicts frequency doublets which have been observed experimentally. A threshold condition of parametric excitation is derived from the region of unstable solutions of Mathieu's equation. This threshold condition relates the amplitude and frequency of the driver transducer to the cavity length and to the absorption per wavelength of the medium. Reasonable agreement between theory and experiment is obtained.

Highly Stabilized Half-Watt IMPATT Oscillator

Abstract: An X-band IMPATT oscillator having a stabilized output power of over 0.5 watt has been developed. The oscillator consists of a main cavity and a directly coupled reaction-type cavity for stabilization. The oscillator has a frequency stability of 2.6x10/sup -5/ over a temperature variation ranging from 0/spl deg/ to 50/spl deg/C and an rms noise deviation of 15 Hz/1-kHz bandwidth at 500 kHz from the carrier. Design considerations have been made concerning the admittance characteristics of the circuit and of the diode to determine preferable circuit conditions for stabilization. The output-power loss due to the stabilization is as small as 0.4 dB. The oscillator is capable of operation in a frequency range of 10.7 to 11.7 GHz.

On the use of second quantization for the calculation of two-centre harmonic oscillator integrals

Abstract: Second quantization of the harmonic oscillator is used to derive two-centre overlap, dipole moment and kinetic energy integrals.

Threshold Calculations for an Optical Parametric Oscillator Employing a Hemispherical Resonator

Abstract: A calculation of optical parametric oscillator threshold has been carried out for an oscillator which employs a hemispherical resonator. The analysis considers the effects of focusing and double refraction, and makes possible the calculation of threshold as a function of the focusing parameter ξ and double‐refraction parameter B. The analysis is similar to that carried out by Boyd and Kleinman for a different class of optical resonators. Their analysis assumes that the pump beam is centered (longitudinally) with respect to the focus of the oscillator pump beam. In a hemispherical resonator, however, only half of the pump‐beam focal region can be utilized because of the resonator configuration. As one would expect, oscillator threshold is higher for the hemispherical case than for the Boyd and Kleinman case. However, the increase is at most a factor of 2 (when beam walkoff is absent, i.e., when B=0), and gradually goes to unity as B increases in size. Thus by using a hemispherical resonator in an optical p...

Parametric amplification of surface acoustic waves

Abstract: A parametric surface‐wave amplifier capable of net terminal gain and an electronic gain of 15 to 25 dB is described. The amplifier consists of a three‐frequency lumped‐element varactor parametric amplifier attached to the electrical port of an interdigital surface‐wave transducer. Less than 2 mW of pump power is required and a bandwidth of about 0.6 % at 106 MHz is achieved.

Tunable high-power low-noise stabilized diode oscillator

Abstract: The invention disclosed is a tunable high-power low-noise stabilized frequency semiconductor diode oscillator unit which comprises a semiconductor diode, suitably a Gunn or Avalanche diode, located within a low-Q-resonant cavity for generating the carrier frequency, f0; and another cavity, tuned to f0 and having a very high-Q-relative to the first cavity, is tightly coupled to the low-Q-cavity. A microwave output passage in the low-Q-cavity is provided for connection of the oscillator output directly to a load; wherein the oscillator provides output powers in excess of 100 milliwatts at frequencies of 9.4 gigaHertz (GHz) with lownoise levels and a stabilization factor of approximately 200. A third cavity is coupled to the high-Q-cavity. The third cavity includes a voltage ''''tunable'''' diode, a varactor which varies in capacitance as a function of applied voltage. This provides a tuner which permits changing the frequency of resonance of the high Q cavity without substantially affecting its Q-value.

Acoustic wave parametric amplifier/converter

Abstract: A parametric device for acoustic waves which does not depend on the non-linearities of a medium for operation. Both degenerate and non-degenerate parametric amplifier/converters are provided in which first order velocity changes give parametric interactions. The electric field associated with an acoustic wave in a piezolectric medium is modulated by an electric pump wave. This is accomplished by modulating the conductivity of a region in the piezoelectric medium, or close to that medium. The resulting modulation of the K-vector of the acoustic wave leads to parametric interactions between the acoustic signal wave, the electric pump wave, and the generated idler wave. Various effects, such as the field effect and the photoconductive effect, are used to modulate the conductivity of the region.

Doppler effect frequency monitoring system

Abstract: The present invention relates to the controlling or piloting of the frequency of a radio oscillator, by a quantum oscillator, or vice-versa The object of the invention is a Doppler effect comparator device comprising means for modulating the optical oscillation produced by the quantum oscillator at a frequency generated by a radio oscillator Interferometric means are provided in order to heterodyne said modulated wave with the modulated wave reflected by a moving obstacle This technique makes it possible to substitute for the comparison of the frequencies received by the comparator, the comparison of the Doppler frequencies which result

Frequency modulation by light impingement on a solid state oscillator

Abstract: Frequency modulation by varying the intensity of light impinging on a three terminal GaAs microwave oscillator.

Electrically and mechanically tunable microwave power oscillator

Abstract: A high efficiency, negative resistance microwave power oscillator is disclosed which is tunable over a wide frequency range by applying a variable voltage to a varactor which is coupled to the resonant cavity of the oscillator and also by varying the size of the cavity as by moving a part of the floor thereof with respect to the negative resistance diode contained in the cavity. The power output and the electronic tuning sensitivity change little over the mechanical tuning range.

Phase matching in dielectric waveguides to extend the interaction distance of harmonic generators and parametric amplifiers

Abstract: The interaction distance in harmonic generators and parametric amplifiers is extended over a sufficiently long distance to effect optimum frequency conversion by forming the nonlinear dielectric medium into a waveguide, and proportioning its crosssectional dimensions such that the relevant waves propagate with the same phase velocity. In an harmonic generator, the waveguide is proportioned such that the applied fundamental frequency wave and the orthogonally polarized, harmonic wave induced in the medium propagate with the same phase velocity. In a parametric amplifier, the applied signal and the induced idler wave propagate with the same polarization, while the pump wave is orthogonally polarized.

Properties of a 15-cm i.d. Multipath CO(2) Laser Amplifier and Oscillator.

Abstract: Several multipath structures have been used for laser oscillators and amplifiers. Off-axis paths in a spherical mirror interferometer have been used to produce a multiplicity of paths in a CO2 amplifier. White-type mirror systems have been used in multipath laser oscillators and amplifiers for He -Ne lasers and for CO2 lasers. In this paper we extend our previous work by making a more detailed investigation of the amplifier characteristics and of the oscillator mode structure in a larger diameter White-type multipath CO2 laser. A multipath structure adapted from that described by Edwards was used. The schematic drawing of this structure in the amplifier configuration is shown in Fig. 1. Corning Glass Works 15.2-cm i.d. flanged glass pipe and 15.2-cm × 5.1-cm i.d. glass crosses were used to construct the cell. Off-axis aluminum disks were used as electrodes. The cathode had a 3.5-cm diam central hole to which a vacuum pump was connected. Axial spacing between electrode centers was 2.74 m. The gas input to the cell was located at the anode end and two 425-liters/min vacuum pumps were used at the cathode end. The mirrors were beral coated quartz with a separation of 3 m. (A minor improvement was obtained when the beral coated mirrors were replaced with gold coated, copper substrate mirrors.) A mask was placed 7 cm in front of the segmented mirrors of the White system in order to prevent self-oscillation in the amplifier configuration and to control the mode structure in the oscillator configuration. The mask, as shown in Fig. 1, was a 14-cm diam anodized aluminum disk with two 1.9-cm diam holes separated by 4.5 cm. The mask was coated with silicone vacuum grease to reduce its reflectivity. In the amplifier configuration, Brewster angle windows of sodium chloride were used at the input and output of the mulipath cell. When the multipath cell was used as an oscillator, one of the Brewster angle sodium chloride windows was removed and replaced by a sodium chloride disk oriented perpendicular to the oscillator cavity axis. A gold front surface reflector was used external to the remaining Brewster angle window. The largest value of amplifier gain was obtained with a discharge current of 100 mA, and flow rates, measured at room temperature and atmospheric pressure, of 4.4 cc/sec CO2, 12 cc/sec N2, and 3.2 cc/sec He. The corresponding pressures measured with a Wallace and Tiernan gauge connected through the end plate supporting the full White mirror were 0.1-Torr CO2, 0.5-Torr N2, and 2.7-Torr He. The voltage across the electrodes was 5.7

Parametric Resonance in Certain Nonlinear Systems

Abstract: In a number of mechanical problems, systems of differential equations with periodic coefficients have to be considered, which, in general, possess not only linear but also nonlinear terms. In this paper, the first order instability region of the Mathieu equation is examined when additional nonlinear terms are present. These terms can be of the damping or restoring type.

Inverter system with resonant electro-dynamical device

Abstract: This invention combines a resonant electrodynamical device with an electromagnetic oscillator that has its period of oscillation syntonized with the natural period of oscillation of the resonant electrodynamical device. In the preferred embodiment, the resonant electrodynamical device is a swing motor connected with a compressor load, and power for driving the swing motor is supplied by the syntonic oscillator. A feedback from the swing motor maintains the oscillator in syntonization with the natural period of oscillation of the swing motor.

Threshold of the optical backward-wave parametric oscillator

Abstract: We present a discussion of the threshold condition for the optical backward-wave parametric oscillator, taking into account diffraction due to the finite transverse extent of the fields, and using three transverse modes of both the forward- and backward-wave fields. The coupled differential equations are solved numerically, and the threshold is obtained by minimizing the pump field with respect to the parameters of the forward- and backward-wave fields. Denoting the confocal parameters by b_{1}, b_{2} , and b 3 for the backward, forward, and pump waves, respectively, and if the length of the crystal is 1, we find that for 1/b_{3} \geq 2 , we may set b_{1} = b_{2} =b_{3} . For most purposes, the phase-matching condition may be taken as k_{2} = k_{1} + k_{3} . Also, when calculating the threshold, it is adequate to consider only the two lowest order transverse modes of the forward-and backward-wave fields.