Investigation of spectral bandwidth of optical parametric amplification

The spectral bandwidth of three-wave-mixing optical parametric amplification has been investigated. A general mathematical model for evaluating the spectral bandwidth of optical parametric amplification is developed with parametric bandwidth and gain bandwidth via three-wave noncollinear interactions. The spectral bandwidth is determined by expanding the wave-vector mismatch in a Taylor series and retaining terms through second order. The model takes into account the effects of crystal length, noncollinear angle, group velocity, group-velocity dispersion and gain coefficient. The relation between parametric bandwidth and gain bandwidth is clearly defined. The model is applied to a BBO OPA, a LBO OPA and a CLBO OPA. PACS 42.65.Yj; 42.65.Lm; 42.65.Ky; 42.60.By     

Double quasi phase matching for both optical parametric oscillator and difference frequency generation

We present simultaneous phase matching of optical parametric oscillator (OPO) and difference frequency generation (DFG), using a noncollinear interaction in periodically poled crystal with single grating. Selecting proper grating period Λ and titled angle ξ between the grating vector G and the optical axis of crystal, the noncollinear scheme provides double phase matching solutions over continuous regions of the midwave infrared spectrum. At certain wavelength regions, for DFG process the group velocities between interaction pulses are matching and the phase matching bandwidth reaches maximum. Selecting the different grating period, the broadband midwave tuning and better gain spectrum can be obtained at different wavelength range. For the certain period grating the conversion efficiency is higher. Hence, using the double phase matching configuration, the broadband tunable midwave infrared wave can be produced in single grating. But the configurations have a relatively narrow angular bandwidth.     

Optical parametric generation and phase matching in magneto-optic media

We derive the equations and main characteristics of optical parametric generation in magneto-optic media. The key performances are discussed in terms of Stokes parameters and conservation laws of electromagnetic linear and angular momentum.     

Dependency of injection seeding and spectral purity of a single resonant KTP optical parametric oscillator on the phase matching condition

For spectroscopic and remote sensing applications injection seeded optical parametric oscillators (OPOs) are well established. In this paper we study the dependencies of signal resonant injection seeding of an OPO on its resonator length, phase matching angle and pump power in detail. The quality of the seeding process is assessed by stabilising the seed laser on a molecular absorption line of water vapour and using a water vapour absorption cell as a narrow bandwidth filter for the injection seeded radiation. A reduction of the acceptance of injection seeding is observed with increasing pump power. For small phase mismatch injection seeding with a spectral purity of 99.7% was observed at 13-fold OPO threshold. A signal pulse energy of 38 mJ with 50% pump depletion was achieved with a beam parameter M² of about 6. PACS 42.65.Yj; 42.79.Nv; 42.79.Qx     

Second harmonic generation by modal phase matching involving optical and plasmonic modes

The feasibility of a modal phase matching scheme between optical modes and surface plasmonic modes is demonstrated: in fact, the high effective index of a plasmonic mode allows us to obtain phase matching even in semiconductors showing a large dispersion between fundamental and second harmonic wavelengths. We design a realistic device to obtain Type-II second harmonic generation in AlGaAs-based waveguides; whereas one of the two pumps is carried by a plasmonic mode, the generated second harmonic signal is guided inside the AlGaAs multilayer, and hence it is not hampered by high propagation losses.     

Collinear broadband optical parametric generation in periodically poled lithium niobate crystals by group velocity matching

Collinear broadband optical parametric generation (OPG) using periodically poled lithium niobate (PPLN) crystals were designed and experimentally demonstrated with the quasi-phase matching (QPM) periods of 21.5, 24.0, and 27.0 μm. The broad gain bandwidth was accomplished by choosing a specific set of the period and the pump wavelength that allows the group velocities of the signal and the idler to match close to the degeneracy point. OPG gain bandwidth and also the spectral region could be controlled by proper design of QPM period and pump wavelength. The total OPG gain bandwidth of 600, 900, and 1200 nm was observed for the PPLN devices with QPM periods of 21.5, 24.0, and 27.0 μm, respectively. We have also observed multiple color visible generation whenever the OPG spectrum was significantly broad. From the visible peaks of the three PPLN samples, it is found that broad gain bandwidth is crucial in the temperature-insensitive collinear simultaneous RGB generation from a single crystal.     

Cavity phase matching via an optical parametric oscillator consisting of a dielectric nonlinear crystal sheet

We experimentally demonstrate cavity phase matching for the first time using a sheet optical parametric oscillator which is made of an x-cut KTiOPO(4) crystal sheet. This microcavity presents 220 kW peak power capability for near-frequency-degenerate parametric outputs with up to 23.8% slope efficiency. It also features unique spectral characteristics such as single-longitudinal-mode and narrow linewidth. These attractive properties predict broad applications of such a mini-device, such as terahertz generation, photonic integration, spectroscopy, and quantum information, etc.     

Enhanced bandwidth noncollinear optical parametric amplification with a narrowband anamorphic pump

Through the use of anamorphic focusing, we present a method for generating broadband noncollinear optical parametric amplification in signal regions lacking a broadband phase-matching condition that is ideally suited for narrowband pump sources, herein based on an erbium-doped fiber oscillator. With a short focal length cylindrical lens to enhance the phase-matching condition and a long focal length cylindrical lens in the orthogonal plane to limit the pump power in the amplifying beta barium borate crystal, we amplify pulses in the blue-green spectral region with over 100 THz (～3500 cm(-1)) bandwidth. The amplified signal is subsequently compressed to 9.5 fs, near the transform limit.     

Design of a diffractive optical element for wide spectral bandwidth

A new method for eliminating the chromatic aberration of a diffractive optical element (DOE) for wideband wavelengths is presented. The wideband-wavelength diffractive optical element (WBDOE) consists of two aligned DOE's. The use of different dispersive materials for the two DOE's eliminates chromatic aberration. The design and simulation of a WBDOE for the visible spectrum are presented.     

Frequency comb generation and carrier-envelope phase control in femtosecond optical parametric oscillators

We describe progress in the measurement and control of the carrier-envelope phase-slip frequencies of pulses generated by a femtosecond optical parametric oscillator. Example applications of such control are presented and include the generation of a frequency comb spanning nearly three optical octaves, and the creation of a train of 30-fs pulses via coherent pulse synthesis. Future prospects for frequency combs based on femtosecond optical parametric oscillators are discussed.     

Numerical calculation of the spectral bandwidth of optical parametric amplification in hybrid organic/inorganic planar waveguide

The spectral bandwidth of three-wave-mixing optical parametric amplification has been investigated in a simple hybrid polymer/ion exchanged planar optical waveguiding structure. A nonlinear polymer is deposited on the top of a glass substrate with a waveguide realized by the ion-exchange technique. The spectral bandwidth is determined by expanding the wave-vector mismatch in a Taylor series and retaining terms through second order. The relation between parametric bandwidth and gain bandwidth is clearly defined.     

Octave phase matching for optical parametric amplification of single-cycle pulses in the mid-infrared range

Analysis of optical properties of mid-infrared-transparent nonlinear crystals reveals octave phase matching for a highly efficient optical parametric amplification of single-cycle electromagnetic field waveforms within the 3- to 12-μm wavelength range, recently demonstrated in experiments.     

Monolithic optical parametric oscillator using chirped quasi-phase matching

We describe a highly efficient monolithic, Q-switched, nanosecond optical parametric oscillator based on a magnesium-oxide-doped periodically poled lithium niobate crystal and containing multiple quasi-phase-matched gratings. The crystal consisted of a single unchirped grating and five gratings containing progressively increasing amounts of longitudinal chirp. The monolithic design makes the device highly compact, stable, and robust, and it demonstrated a pump-to-signal conversion efficiency of around 50%, generating 50 microJ pulses at 1.55 microm with a spectral bandwidth of 20 nm. Sonogram traces are presented showing the effect of crystal chirp on the temporal and spectral performance.     

Infrared laser generation by cascaded difference frequency generation combined with optical parametric oscillator

Optical Review - We introduce an infrared laser generation scheme by cascaded difference frequency generation (CDFG) combined with optical parametric oscillator (OPO). An inventive infrared laser...     

Efficient second harmonic generation by a femtosecond pulse far from phase matching

Highly efficient second harmonic generation by a femtosecond pulse under the condition of group matching in the absence of phase matching was obtained. Second-order dispersion and cubic nonlinearity of the propagation medium were considered. The cubic nonlinearity is necessarily required for the generation to be efficient. The results obtained open up a fundamental opportunity for the efficient cascade generation of optical harmonics to be realized.     

Achromatic phase matching for tunable second-harmonic generation by use of a grism

Achromatic phase matching (APM) involves dispersing the light entering a nonlinear-optical crystal so that a wide range of wavelengths is simultaneously phase matched. Using an APM arrangement consisting of a grism (a grating on the surface of a prism) and three prisms, optimized to match a second-harmonic crystal phase-matching angle versus wavelength to high order, we efficiently doubled tunable fundamental light near 650nm with a bandwidth of >95 nm by use of a 4-mm type I beta-barium borate crystal. APM uses no moving parts, and unlike previous APM designs, ours avoids lenses and hence is easy to align and insensitive to translational misalignment of the beam.     

Seeded supercontinuum generation with optical parametric down-conversion

The transition between modulation instability gain and induced soliton fission in nonlinear fiber is experimentally investigated by coherent seeding with the two-color output of an optical parametric oscillator. This approach produces supercontinuum spectra displaying persistent, fine modulation from seeding-induced noise reduction. Numerical simulations support the findings.     

Broadband optical frequency comb generation with a phase-modulated parametric oscillator

We introduce a novel broadband optical frequency comb generator consisting of a parametric oscillator with an intracavity electro-optic phase modulator. The parametric oscillator is pumped by 532-nm light and produces near-degenerate signal and idler fields. The modulator generates a comb structure about both the signal and the idler. Coupling between the two families of modes results in a dispersion-limited comb that spans 20 nm (5.3 THz). A signal-to-noise ratio of >30 dB in a 300-kHz bandwidth is observed in the beat frequency between individual comb elements and a reference laser.     

All-optical control of the carrier-envelope phase with multi-stage optical parametric amplifiers verified with spectral interference

Intense ultrashort laser pulses with stabilized carrier-envelope phase (CEP) are generated at 800 nm by using multi-stage collinear and non-collinear optical parametric amplifiers (OPAs). The first-stage collinear OPA is directly pumped by the fundamental-wave pulses and tuned to generate idler pulses at 1600 nm, which are further amplified by a second-stage collinear OPA, and then frequency-doubled to generate CEP-stabilized pulses at 800 nm. A non-collinear OPA is used to amplify the CEP-stabilized pulses at 800 nm. The combination of different OPAs can generate and amplify CEP-stabilized pulses at 800 nm without any detrimental influence from the fundamental-wave pulses. The CEP stabilization is verified with a simple and robust spectral interference setup. The stable interference pattern is measured for every single pulse and compared with the unstable pattern from pulses of random CEP. PACS 42.65.Re; 42.65.Yj; 42.25.Kb     

Widely tunable optical parametric generation in a photonic crystal fiber

We report on the observation of widely tunable optical parametric generation in a photonic crystal fiber. The frequency shift of the generated sidebands that arise from modulational instability is strongly dependent on the detuning of the pump from the fiber's zero-dispersion wavelength. We are able to demonstrate experimentally more than 450 nm of sideband tunability as we tune the pump wavelength over 10 nm. Excellent agreement has been found between the experimentally measured and theoretically predicted shifts.