Femtosecond self-doubling optical parametric oscillator based on KTiOAsO4

Cataloged from PDF version of article.We report a femtosecond intracavity-frequency-doubled optical parametric oscillator that employs a single KTiOAsO4 crystal for both parametric generation and frequency doubling. This device generates a yellow output beam at 575 nm with 39.4% power conversion efficiency when synchronously pumped by a femtosecond Ti :sapphire laser at a wavelength of 796 run. An intracavity retarder is employed to alleviate temporal pulse overlap problems associated with group velocity mismatch inside the KTiOAsO4 crystal

Non-orthogonal Domains in Phase Space of Quantum Optics and their relation to fractional Fourier transform

Cataloged from PDF version of article.It is customary to define a phase space such that position and momentum are mutually orthogonal coordinates. Associated with these coordinates, or domains, are the position and momentum operators. Representations of the state vector in these coordinates are related by the Fourier transformation. We consider a continuum of “fractional” domains making arbitrary angles with the position and momentum domains. Representations in these domains are related by the fractional Fourier transformation. We derive transformation, commutation, and uncertainty relations between coordinate multiplication, differentiation, translation, and phase shift operators making arbitrary angles with each other. These results have a simple geometric interpretation in phase space and applications in quantum optics

Plane-wave theory of self-doubling optical parametric oscillators

Cataloged from PDF version of article.This paper presents a theoretical analysis of selfdoubling optical parametric oscillators (OPO’s) where a single nonlinear crystal is used for both parametric generation and frequency doubling. In these devices, the parametric generation and frequency-doubling processes are both phase matched for the same direction of propagation inside the crystal. Different polarization geometries for which this simultaneous phasematching condition can potentially be satisfied are identified and categorized. Plane-wave coupled-mode equations are presented for each of these categories. Numerical solutions of these coupledmode equations and calculation of the single-pass saturated signal gain are outlined. Intracavity signal photon flux calculations based on these numerical solutions are presented. The dependence of performance measures such as the photon conversion efficiency on various design parameters are investigated

Analysis of the generation of amplitude-squeezed light with Gaussian-beam degenerate optical parametric amplifiers

Cataloged from PDF version of article.We investigate the generation of amplitude-squeezed states with degenerate optical parametric amplifiers that are pumped by focused Gaussian beams. We present a model that facilitates the calculation of the squeezing level for an experimentally realistic cofiguration in which there is a Gaussian input signal beam that has the same confocal parameter and waist location as the Gaussian pump beam, with no restriction on the interaction length-to-confocal parameter ratio. We show that the 3-dB squeezing limit that was thought to be imposed by the Gaussian pump profile can be exceeded in the (previously uninvestigated) tight-focusing regime. We find the maximum possible amplitude squeezing in this regime to be 4.65 dB. However, it is possible to increase the squeezing level further by spatially filtering the tails of the output signal beam, resulting in squeezing levels in excess of 10 dB. (C) 2001 Optical Society of America

Simultaneous phase matching of optical parametric oscillation and second harmonic generation in a periodically-poled lithium niobate

Cataloged from PDF version of article.We report a simple ad hoc method for designing an aperiodic grating structure to quasi-phase match two arbitrary second-order nonlinear processes simultaneously within the same electric-field-poled crystal. This method also allows the relative strength of the two processes to be adjusted freely, thereby enabling maximization of the overall conversion efficiency. We also report an experiment that is based on an aperiodically poled lithium niobate crystal that was designed by use of our method. In this crystal, parametric oscillation and second-harmonic generation are simultaneously phase matched for upconversion of a femtosecond Ti:sapphire laser to 570 nm. This self-doubling optical parametric oscillator provides an experimental verification of our design method. © 2003 Optical Society of Americ

Phase matched self-doubling optical parametric oscillator

Cataloged from PDF version of article.We report a synchronously pumped intracavity frequency-doubled optical parametric oscillator that employs a single KTiOPO4 crystal for both parametric generation and frequency doubling. Both nonlinear processes are phase matched for the same direction of propagation in the crystal. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 745 nm, generates a green output beam at 540 nm with a 29% power conversion efficiency. Angle tuning in conjunction with pump wavelength tuning provides output tunability in the 530–585-nm range. 1997 Optical Society of Americ

Multimode pumping of optical parametric oscillators

Cataloged from PDF version of article.Calculations suggest that optical parametric oscillators (OPO’s) can be efficiently pumped using multimode, divergent pump sources. The influence of pump beam divergence and mode structure upon OPO performance is measured for both noncritical phase-matching, and OPO’s with walkoff. Multimode OPO pumping is shown to be efficient, provided appropriate nonlinear crystals and OPO cavities are employed; the nonlinear crystal must have sufficient angular acceptance to tolerate a divergent pump; the OPO cavity must support modes that match the divergence and spatial intensity characteristics of the pump. For low-order pump modes, the OPO can be made to match the mode of the pump. Higher order pump modes reduce the OPO efficiency, and cause a saturation of efficiency with increasing pump power. The efficiency is degraded in a similar fashion in the presence of walkoff. Multimode pumping is more difficult in longer OPO cavities due to increased buildup time of higher order OPO modes

Single-crystal sum-frequency-generating optical parametric oscillator

Cataloged from PDF version of article.We report a synchronously pumped optical parametric oscillator that generates the sum frequency of the pump and the signal wavelengths. A single KTiOPO4 (KTP) crystal is used for both parametric generation and sum-frequency generation in which these two processes are simultaneously phase matched for the same direction of propagation. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 827 nm, generates a blue output beam at 487 nm with 43% power-conversion efficiency. The polarization geometry of simultaneous phase matching requires rotation of the pump polarization before the cavity. Adjusting the group delay between the two orthogonally polarized pump components to compensate for the group-velocity mismatch in the KTP crystal increases the photon-conversion efficiency more than threefold. Angle tuning in conjunction with pump wavelength tuning provides output: tunability in the 484-512-nm range. A planewave model that takes group-velocity mismatch into account is in good agreement with our experimental results. (C) 1999 Optical Society of America [S0740-3224(99)01309-0]

Solar-blind AlGaN-based Schottky photodiodes with low noise and high detectivity

Cataloged from PDF version of article.We report on the design, fabrication, and characterization of solar-blind Schottky photodiodes with low noise and high detectivity. The devices were fabricated on n-/n+ AlGaN/GaN heterostructures using a microwave compatible fabrication process. True solar-blind operation with a cutoff wavelength of similar to274 nm was achieved with Al(x)Ga(1-x)N (x=0.38) absorption layer. The solar-blind detectors exhibited <1.8 nA/cm(2) dark current density in the 0-25 V reverse bias regime, and a maximum quantum efficiency of 42% around 267 nm. The photovoltaic detectivity of the devices were in excess of 2.6x10(12) cm Hz(1/2)/W, and the detector noise was 1/f limited with a noise power density less than 3x10(-29) A(2)/Hz at 10 kHz. (C) 2002 American Institute of Physics

High-Speed InSb Photodetectors on GaAs for Mid-IR Applications

Cataloged from PDF version of article.We report p-i-n type InSb-based high-speed photodetectors grown on GaAs substrate. Electrical and optical properties of photodetectors with active areas ranging from 7.06 x 10(-6) cm(2) to 2.25 x 10(-4) cm(2) measured at 77 K and room temperature. Detectors had high zero-bias differential resistances, and the differential resistance area product was 4.5 Omega cm(2). At 77 K, spectral measurements yielded high responsivity between 3 and 5 mum with the cutoff wavelength of 5.33 mum. The maximum responsivity for 80-mum diameter detectors was 1.00x10(5) V/W at 4.35 mum while the detectivity was 3.41x10(9) cm Hz(1/2) /W. High-speed measurements were done at room temperature. An optical parametric oscillator was used to generate picosecond full-width at half-maximum pulses at 2.5 mum with the pump at 780 nm. 30-mum diameter photodetectors yielded 3-dB bandwidth of 8.5 GHz at 2.5 V bias