Showing papers on "Parametric oscillator published in 1974"

Second harmonic generation and infrared mixing in AgGaSe2

Abstract: We have continuously tuned between 7 and 15 μm by mixing the output of a LiNbO3 parametric oscillator in the chalcopyrite AgGaSe2 We have doubled a CO2 laser with 27% efficiency which agrees very well with the expected efficiency and verifies the high optical quality of the 153‐cm‐long AgGaSe2 crystal The measured transparency range, indices of refraction, and nonlinear coefficient of d36 = (37 ± 06) × 10−11 m/V show that AgGaSe2 is a useful infrared nonlinear material phase matchable over the entire 3–18‐μm infrared region

A 1.4–4‐μm high‐energy angle‐tuned LiNbO3 parametric oscillator

Abstract: We have operated a high‐gain angle‐tuned singly resonant LiNbO3 parametric oscillator pumped directly at 1.06 μm by a Q ‐switched Nd:YAG laser. The oscillator angle tunes from degeneracy and operates over the entire 1.4–4.4‐μm range. Output energies of greater than 1 mJ/pulse at 5 pps have been observed with a 15% energy conversion efficiency. The key to this device is the large LiNbO3 crystals fabricated from new [01.4] grown boules. Crystals up to 15 mm in diameter and 5 cm in length have been cut at the nominal 47° orientation. These crystals will potentially handle over 2 J of optical energy at 1.06 μm.

Singly resonant CdSe parametric oscillator pumped by an HF laser

Abstract: A transverse excitation HF laser has been used to pump a singly resonant CdSe infrared parametric oscillator. Tunable output has been generated over the range 4.3–4.5 μm and 8.1–8.3 μm with peak powers of up to 800 W. By a combination of angle tuning and selection of HF pump wavelength, CdSe is phase matchable for generation of radiation from 3.0–4.8 μm and 7.8–22 μm.

Phase‐matched second‐harmonic generation in GaAs optical waveguides by focused laser beams

Abstract: Using a tunable parametric oscillator operating near 2 μm, we have observed second‐harmonic generation in a GaAs double‐heterostructure waveguide in the region of phase matching. The harmonic intensity is strongly peaked when the guide propagation constants of the TE (m=0) fundamental and TM (m=2) harmonic are equal. Away from phase matching, the characteristic effects of strong focusing in the plane of the guide are observed. These are the one‐dimensional analogs of the harmonic generation effects observed using two‐dimensional focused laser beams.

Amplification of microwaves by superconducting microbridges in a four‐wave parametric mode

Abstract: We have observed an electronic gain of 12 dB at 10 GHz in a parametric amplifier whose nonlinear element is a series of unbiased Anderson‐Dayem microbridges. The bandwidth was measured to be 1 GHz and the noise temperature to be less than 20 K.

Enhancing chemical reactions

Abstract: Methods of enhancing selected chemical reactions. The population of a selected high vibrational energy state of a reactant molecule is increased substantially above its population at thermal equilibrium by directing onto the molecule a beam of radiant energy from a laser having a combination of frequency and intensity selected to pump the selected energy state, and the reaction is carried out with the temperature, pressure, and concentrations of reactants maintained at a combination of values selected to optimize the reaction in preference to thermal degradation by transforming the absorbed energy into translational motion. The reaction temperature is selected to optimize the reaction. Typically a laser and a frequency doubler emit radiant energy at frequencies of ν and 2ν into an optical dye within an optical cavity capable of being tuned to a wanted frequency δ or a parametric oscillator comprising a non-centrosymmetric crystal having two indices of refraction, to emit radiant energy at the frequencies of ν, 2ν, and δ (and, with a parametric oscillator, also at 2ν-δ). Each unwanted frequency is filtered out, and each desired frequency is focused to the desired radiation flux within a reaction chamber and is reflected repeatedly through the chamber while reactants are fed into the chamber and reaction products are removed therefrom.

Digitally controlled oscillator using semiconductor capacitance elements

Abstract: The tuned circuit of an oscillator includes n metal-insulator-semiconductor (MIS) diodes. The oscillator frequency may be switched, in discrete steps, to any one of 2n different values in response to n control voltages, representing an n bit binary word, applied to the respective diodes.

Multiple parametric resonance in a non-linear two degree of freedom system

Abstract: A non-linear two degrees of freedom dynamical system subjected to parametric excitation is studied. The relationship between the parametric frequency and the natural frequencies of the system are such that the first generalized coordinate is excited into parametric resonance while both generalized coordinates are excited into combination resonance at the same time. The unstable zone and response of the system under multi-resonant condition are then compared with the unstable zones and responses of the system where each type of resonance is treated on an individual basis, assuming the other type of resonance does not occur.

Exact evaluation of a path integral relating to an electron gas in a random potential

Abstract: The path integral of an oscillator with memory occurring in the theory of an electron gas in a random potential is evaluated exactly. The analysis simply reduces the problem to that of averaging the propagator of a forced harmonic oscillator using a gaussian probability for the external force.

Current limited oxcillator arrangement

Abstract: A current limiting oscillator circuit for a low pressure electric discharge lamp wherein an oscillator means is coupled to a DC potential source and to a load circuit coupled to the DC potential source with a current sampling means coupled to the oscillator means and a switching means coupling the current sampling means to the oscillator means whereby the switching means limits the current flow and renders the oscillator means non-conductive while the load circuit renders the oscillator means conductive.

Electronic tuning of stable transferred electron oscillators

Abstract: The problem of electronic tuning of microwave osciilator structures characterized by high energy storage and hence low noise is considered. The evolution of a wide-band varactor tuned J-band oscillator is described, and analytical criteria are presented which determine the position of the varactor diode and the theoretical maximum tuning range available including Varactor loss. Experimental results confirm the validity of the circuit model used for the proposed oscillator structures.

The dynamic stability of degenerate systems under parametric excitation

Abstract: The parametric resonance in a system having two modes of the same frequency is studied. The simultaneous occurence of the instabilities of the first and second kind is examined, by using a generalized perturbation procedure. The region of instability in the first approximation is obtained by using the Sturm's theorem for the roots of a polynomial equation.

Characteristics of the Optical Parametric Oscillator and Its Use for Selective Excitation

Abstract: Techniques are presented for obtaining stable, single mode output from an optical parametric oscillator and for aligning such an oscillator with a molecular or atomic transition. A line width of 10(-3) cm(-1) or less was obtained with a long term frequency stability of 10(-3) cm(-1) or better. It has been demonstrated that an OPO can stay aligned for several hours with an absorption line of half-width 0.01 cm(-1).

Solid state microwave cavity oscillator operating below cavity cutoff frequency

Abstract: A microwave oscillator using a Gunn diode in a section of rectangular waveguide tuned to resonate as a cavity to a fundamental frequency that is below the waveguide cutoff frequency has its output for the fundamental frequency located at a place in the cavity at which a peak of the fundamental frequency wave and a null of the second harmonic coincide. Fundamental frequency output is taken in a direction transverse to the axis of the waveguide. Harmonic frequency energy can also be taken from the waveguide section, or suppressed, as desired.

Algebraic-numerical method for the slightly perturbed harmonic oscillator

Abstract: The solution of slightly perturbed harmonic oscillators can easily be obtained in the form of a series given by Poisson's method. However, this perturbation method leads to secular terms unbounded for large time (the time unit being the fundamental period of the harmonic oscillator), which prevent the use of finite series. The analytical elimination of such terms was first solved by Poincare and, more recently, generalized by Krylov and Bogoliubov. Unfortunately, these methods are very difficult to handle and are not easily carried out for high orders. A numerical reinitialization method is combined here with the Poisson perturbation treatment to avoid the growth of secular terms and therefore to get the solution at any time. The advantages of such a method is that the analytical work can be carried to high orders keeping the step of numerical integration to a relatively large value (compared to a purely numerical method). This algorithm has been tested on the Mathieu equation. A method for the computation of the eigenvalues of this equation is given. By properly selecting the order of the perturbation and the time step of reinitialization, we can recover, at any order, all the effects of the slight perturbation (including all the unstable zones). Consequently, such a method is a useful intermediate between purely analytical and purely numerical algorithms.

Modulated transistor oscillators

Abstract: A transistor oscillator wherein output power does not vary with frequency modulation and wherein output frequency does not vary with amplitude modulation. These results are achieved by controlling the phase shift properties of a junction transistor where phase shift properties depend upon the transit time of carriers through the transistor. The transit time is a function of the emitter current and the collector-to-base voltage operating points and the frequency of oscillation of the oscillator circuit depends upon this transit time. Also, the output power of the oscillator is a function of the emitter current and collector-to-base voltage operating points. By simultaneously varying both of these operating points, the frequency of the oscillator can be varied without changing the power output and the output power can be varied without changing the frequency.

Tunable electromagnetic oscillator using {8 01.4{9 {0 grown linbo{hd 3 {b and method

Abstract: This invention relates to a unique high energy, pulsed, widely tunable, coherent oscillator based on an angle-tuned 1.06 mu m pumped LiNbO3 parametric oscillator. The oscillator's basic 1.4 mu m to 4.4 mu m frequency range is extended to the visible and ultraviolet by second harmonic and sum frequency generation in LiNbO3, LiIO3, and KDP. The parametric oscillator source is estimated to be 30% efficient when pumped with a 10 mJ per pulse or 300 mJ per pulse Nd:YAG laser. Similarly, the following mixing and sum generation steps are also shown to be nearly 30% efficient. The parametric oscillator followed by a crystal of AgGaSe2, CdSe, or LiNbO3 thus efficiently tunes over a spectral range between 0.62 mu m and 27 mu m. Since all processes are angle phasematched, the tuning rate is rapid.

Low-Cost X-Band MIC Parametric Amplifier

Abstract: An X-band MIC parametric amplifier using planar printed circuit techniques which result in low-cost and high reliability has been developed. Design of a microstrip four-port circulator and parametric amplifier stage on a low-loss YIG substrate, a 31-GHz microstrip pump source on teflon-fiber glass, and a pump source at the same frequency in integrated fin-line are described.

Circuit arrangement for digital frequency indication in a radio receiver

Abstract: In a circuit arrangement for digitally indicating the tuned frequency of a radio receiver operating in the AM and FM ranges in which the oscillations of the AM tuning oscillator and of the FM tuning oscillator are amplified, converted to rectangular oscillations, counted by means of electronic counters and then digitally displayed, the oscillations of the AM tuning oscillator and the oscillations of the FM tuning oscillator are amplified by a common broadband amplifier which is sufficiently broadbanded so that the oscillator frequencies for the AM range as well as those for the FM range are both passed and amplified and the coupling of the input of the broadband amplifier to the outputs of the tuning oscillators is so loose that the tuning oscillators are not noticeably detuned by changes in capacity in the broadband amplifier.

A Design Theory for Wide-Band Parametric Amplifiers

Abstract: A new exact design theory for a nondegenerate parametric amplifier with double-tuned signal circuit and single-tuned idler circuit is described. If the resistance of the signal circuit, which is neglected in previous papers, is considered, there exists a frequency band in which the amplifier gain is positive. In this paper the band characteristics of the gain are related to this frequency band. Slope parameters of the idler and signal circuits are normalized by the slope parameters which are associated with the diode itself. These normalized slope parameters are used to relate the actual circuit and gain-bandwidth characteristics. The slope parameter of the external signal resonator is related to the negative slope parameter of the diode, and bounds on this ratio are given over which stable amplification is possible. A design table which gives the coupling ratio and slope parameter of the external signal resonator is derived by computer calculation. Experiments were made at 19 GHz. Positive-gain bandwidth was around 4.0 GHz, and flat bandwidth at 10-dB gain was 2.4 GHz. The ratio of these bandwidths coincided with the theory.

Direct reading microwave refractometer

Abstract: A microwave refractometer is disclosed which produces an output signal which varies as a linear function of the index of refraction of a microwave resonant sampling cavity. A voltage controlled oscillator having a variable oscillation frequency is electrically coupled to sampling cavity having a variable resonance frequency which is an inverse function of the index of refraction of the cavity. The resonant microwave electromagnetic signal present in the cavity is electrically coupled to a means which varies the oscillation frequency of the voltage controlled oscillator as a function of the resonant frequency and index of refraction of the sampling cavity. Means electrically coupled to an output signal of the voltage controlled oscillator produce an output signal which varies as a linear function of the index of refraction of the sampling cavity. In the preferred embodiment, this means comprises a crystal oscillator having a stable oscillation frequency and a circuit electrically coupled between the output of the voltage controlled oscillator and the crystal oscillator for gating and counting the number of cycles of the crystal oscillator which occur during a time interval which is a linear function of the index of refraction of the sampling cavity.

Measurement of the geomagnetic field using parametric resonances in optically pumped He 4

Abstract: A single-axis vector magnetometer which can be used to measure changes in geomagnetic field components has been constructed using a parametric resonance in the optically pumped 23S 1 level of He4. The principle of operation for the n=1, p=1 parametric resonance is described. This resonance has a peak amplitude-to-noise ratio of 1.2 \times 10^{4} in a 0.5 Hz noise bandwidth and a 14.9 \times 10^{-4} G linewidth. The performance of the instrument is demonstrated by observing changes in the earth's field and 1.0μG calibration signals. Sensitivity is established to be 1.0 \times 10^{-7} G in a 5 Hz noise bandwidth.

Parametric excitation of a plasma instability by modulation of its damping coefficient

Abstract: Results are presented which show that a previously damped ion-sound instability ( omega 0) can be parametrically excited in a plasma by modulating the damping coefficient at a frequency omega 1 approximately=2 omega 0. In this case, the damping coefficient is varied between a positive value and a negative value, and, in fact, this coefficient must be negative for some fraction of a cycle, for parametric excitation to occur. It is found that a certain threshold modulation depth, h, is required before parametric excitation occurs. At larger values of h, a classical symmetrical parametric resonance curve (instability amplitude versus frequency) is observed. However, at very large values of h, non-linear behaviour is apparent. In this case, the parametric resonance curve becomes asymmetric and the non-linear phenomena of 'jumps' and its associated hysteresis effect is observed. A theory developed to describe this ion-sound instability under various conditions, is compared with the experimental results, and good qualitative agreement is obtained.

Broadband low noise parametric amplifier

Abstract: The specification discloses a low noise parametric amplifier for use with a radar receiver. A Gunn diode oscillator is provided to generate a pump frequency. A bandpass filter filters the pump frequency and applies the pump power through a waveguide having a reduced height portion employing a multisection Chebycheff transformer. A coaxial signal input line connects through the waveguide to a coaxial idler section which is provided to terminate the signal input line and to match the signal and idler frequencies. A varactor diode assembly is mounted on the center conductor of the signal input line and the idler section. A cup member is attached to the diode assembly for matching the parallel resonance of the diode assembly to the pump frequency.

Non-equilibrium heating-up of thermal phonons in a dielectric by microwave field

Abstract: The investigation of the noise characteristics of a microwave parametric amplifier with ferroelectric nonlinear elements has shown that the noise temperature of such elements under the high microwave pumping was much higher than the equilibrium temperature of the material. The dependence of the noise temperature of the ferroelectric element, a SrTiO3 film, on the frequency and the pumping voltage has been obtained at a temperature of 78°K. The parametric mechanism of thermal acoustic phonon excitation was proposed for the explanation of the observed phenomena.

Pulse saturation in a traveling wave parametric amplifier

Abstract: The pulse saturation on a nondispersive traveling wave parametric amplifier is solved in the slowly varying approximation with space and time by reducing the dynamic equations to a degenerate form-of the sine-Gordon equation. If the group velocity of the signal wave differs from that of the pump and idler waves, the signal wave obeys the sine-Gordon equation.