Optical Parametric Oscillator Amplifier Research Articles

Diagnostic NH and OH Vibrations for Oxazolone and Diketopiperazine Structures: b2 from Protonated Triglycine

We present infrared multiple photon dissociation (IRMPD) spectra in the hydrogen stretching region of the simplest b fragment, b(2) from protonated triglycine, contrasted to that of protonated cyclo(Gly-Gly). Both spectra confirm the presence of intense, diagnostic vibrations linked to the site of proton attachment. Protonated cyclo(Gly-Gly) serves as a reference spectrum for the diketopiperazine structure, showing a diagnostic O-H(+) stretch of the protonated carbonyl group at 3585cm(-1). Conversely, b(2) from protonated triglycine exhibits a strong band at 3345cm(-1), associated with the N-H stretching mode of the protonated oxazolone ring structure. Other weaker N-H stretches can also be discerned, such as the amino NH(2) and amide NH bands. These results demonstrate the usefulness of the hydrogen stretching region, and hence benchtop optical parametric oscillator/amplifier (OPO/A) set-ups, in making structural assignments of product ions in collision-induced dissociation (CID) of peptides.

Hybrid quadrupole mass filter/quadrupole ion trap/time-of-flight-mass spectrometer for infrared multiple photon dissociation spectroscopy of mass-selected ions

We present a laboratory-constructed mass spectrometer optimized for recording infrared multiple photon dissociation (IRMPD) spectra of mass-selected ions using a benchtop tunable infrared optical parametric oscillator∕amplifier (OPO∕A). The instrument is equipped with two ionization sources, an electrospray ionization source, as well as an electron ionization source for troubleshooting. This hybrid mass spectrometer is composed of a quadrupole mass filter for mass selection, a reduced pressure (∼10(-5) Torr) quadrupole ion trap (QIT) for OPO irradiation, and a reflectron time-of-flight drift tube for detecting the remaining precursor and photofragment ions. A helium gas pulse is introduced into the QIT to temporarily increase the pressure and hence enhance the trapping efficiency of axially injected ions. After a brief pump-down delay, the compact ion cloud is subjected to the focused output from the continuous wave OPO. In a recent study, we implemented this setup in the study of protonated tryptophan, TrpH(+), as well as collision-induced dissociation products of this protonated amino acid [W. K. Mino, Jr., K. Gulyuz, D. Wang, C. N. Stedwell, and N. C. Polfer, J. Phys. Chem. Lett. 2, 299 (2011)]. Here, we give a more detailed account on the figures of merit of such IRMPD experiments. The appreciable photodissociation yields in these measurements demonstrate that IRMPD spectroscopy of covalently bound ions can be routinely carried out using benchtop OPO setups.

CHAPS: a new precision laser-spectroscopic technique

We present a new technique for high-resolution pulsed spectroscopy that employs optical heterodyne detection to determine the instantaneous frequency of individual optical pulses, together with a frequency-binning method to generate high-precision spectra. We further demonstrate that active tuning of the light source is not necessary if the inherent frequency jitter of the source spans the spectral region of interest. This heterodyneassisted approach to coherent pulsed spectroscopy (CHAPS) is applied in real time by using output from a pulsed, injection-seeded optical parametric oscillator–amplifier (OPO–OPA) system, the optical bandwidth of which is characterized via two-photon excitation of the 6S–8S transition in cesium. The resulting sub-Doppler measurements demonstrate the utility of CHAPS as a high-resolution spectroscopic technique and confirm that the pulsed OPO–OPA system operates very close to the Fourier-transform limit. © 2006 Optical Society of America OCIS codes: 020.4180, 040.2840, 120.6200, 190.4970, 230.4320, 300.3700, 300.6320, 300.6410.

Single-mode near-infrared optical parametric oscillator amplifier based on periodically poled KTiOPO_4

A singly resonant, single-axial-mode, optical parametric oscillator (OPO) based on periodically poled KTiOPO4 (PPKTP) is reported. Signal (1.68 micron) and idler (2.90 micron) optical bandwidths have been narrowed to <400 MHz by use of a diffraction grating at grazing incidence. The OPO generates 370 microJ of signal radiation when pumped by 3.1 mJ of 1.064-micron radiation. We implemented a single-pass PPKTP amplifier to yield 2.15-mJ signal and 1.17-mJ idler radiation without broadening the spectral bandwidths.

Tunable Near-Infrared and Visible All-Solid-State Optical Parametric Oscillator Amplifier System Based on Potassium Titanyl Phosphate Crystal

We present the design details and performance characteristics of a low-energy all-solid-state near-infrared optical parametric oscillator amplifier (OPOA). The pump source is a laser diode (LD) pumped frequency-doubled Nd:YAG laser with a single mode energy of 4 mJ in 8 ns, 50 Hz pulses. The OPOA system, based on potassium titanyl phosphate (KTP) crystal, features a low pump energy threshold at 532 nm of less than 0.4 mJ, broad tunability from 750 to 1040 nm for the signal and a conversion efficiency of 27% at 920 nm. External cavity second harmonic conversion of the idler to visible green-red light in a type II KTP crystal and of the signal to visible blue-green light in a type I BBO crystal was performed with efficiencies up to 10%. We have used the near-infrared output for wavelength-dependent fluorescence lifetime studies in ytterbium-doped laser materials. We have also used the second harmonic wavelengths between 565–600 nm to measure the transmission of Nd:YAG in a preliminary experiment to demonstrate the utility of the system.

Bandwidth Narrowing of an All-Solid-State Optical Parametric Oscillator Amplifier System

An all-solid-state narrow-bandwidth tunable near-infrared KTP optical parametric oscillator amplifier (OPOA) is presented. The bandwidth at 960 nm was reduced from the free running mode ( >100 GHz) to less than 150 MHz by the simultaneous injection seeding of the pump laser and the OPOA, which is close to the Fourier transform limit of the 4 ns output pulses. The OPOA has a potential tunability of over 60 nm from 915–975 nm determined by its external cavity grating tuned diode seed laser.

Optical parametric amplifiers: a discrete dynamical model of singly resonant operation leading to a novel approach to the design of systems for high-efficiency amplification

A simple plane-wave model of pulsed, singly resonant, optical-parametric-oscillator and optical-parametric-oscillator-amplifier operation leads to a description of such systems in terms of a discrete dynamical system. The theoretical limits on conversion efficiencies derivable from this model were explored. Analysis of the model for an optical parametric oscillator-amplifier (OPOA) indicates that the effect that backconversion has in limiting efficiency can be avoided if one precisely shapes the time profile of the pump pulse and combines it with an OPOA that is Q switched. For a case of type I phase matching with β-barium borate with a specific pump profile and a 65-mJ input pulse, under the assumption of small absorption, the following are demonstrated: (l) the theoretical possibility of amplification to a few joules at quantum efficiencies higher than 90% and (2) the possibility of amplification to approximately 1 J at an energy efficiency near 45% in a configuration satisfying realistic stress constraints. Pulse widths are in the nanosecond range, and spot sizes are in the millimeter range. Issues of implementation are discussed.

High-repetition-rate femtosecond optical parametric oscillator–amplifier system near 3 μm

An ultrafast laser system for the chemically important 3-μm spectral region has been constructed by means of noncritically phased-matched KTiOPO4 optical parametric gain elements. An optical parametric oscillator, synchronously pumped by a mode-locked Ti:sapphire oscillator, generates high-quality seed pulses for an optical parametric amplifier. The optical parametric amplifier, pumped by a high-repetition-rate Ti:sapphire regenerative amplifier, amplifies the seed pulses by a factor of 520. Pulses with an energy of 550 nJ and a pulse width of 160 fs are produced at a 250-kHz repetition rate in the 3-μm region.

Efficient low-energy near-infrared KTiOPO_4 optical parametric converter

We report a widely tunable near-infrared holosteric KTiOPO(4) optical parametric converter featuring a low pump energy threshold and high conversion efficiency. The converter uses two 10-mm-long crystals in a simple optical parametric oscillator amplif ier configuration and is tunable from 750 to 1040 nm for the signal. The pump energy threshold at 920 nm is 0.44 mJ for the 532-nm 8-ns 50-Hz input. The system produces as much as 0.45 mJ of energy at 920 nm with an external pump-to-signal energy conversion efficiency of 27% for pump inputs from just two times the threshold value. The internal pump-to-signal and idler energy conversion efficiency is estimated to be 58%. The low pump energy requirement of this system makes it compatible with small laser-diode-pumped solid-state lasers.