Valdas Pasiskevicius

Narrowband bulk Bragg grating optical parametric oscillator

A narrowband, pulsed optical parametric oscillator (OPO) whose output coupler is a bulk glass Bragg grating is demonstrated. The OPO is based on periodically poled KTiOPO4 and is pumped by a pulsed, frequency-doubled Nd:YAG laser at 532 nm, generating a signal at 975 nm with a total efficiency of 35%. This novel and compact device shows a spectral bandwidth of 0.16 nm (50 GHz), a decrease by a factor of 20 compared with that when a conventional mirror is used. By using a folded cavity, we demonstrate tunable radiation with a tuning range of 60 nm and maintained spectral bandwidth.

Second-order nonlinearities in the domain walls of periodically poled KTiOPO4

The domain wall regions in periodically poled KTiOPO4 crystals were examined and found to give rise to phasematched second harmonic generation in the Cerenkov directions. This phenomenon is caused by the nonlinear coefficients d11 and d12, which are not present in single domain regions, but are nonzero at and close to domain walls. The appearance of these nonlinearities is attributed to strain, produced by the domain inversion process and results in the creation of a dc piezoelectric field.

Real-time and in situ monitoring of ferroelectric domains during periodic electric field poling of KTiOPO4

We demonstrate a photographic method to view the inversion of ferroelectric domains during the periodic electric field poling of KTiOPO4 by taking advantage of the electro-optic effect and a high speed charge coupled device (CCD) camera. The method is noninvasive and allows monitoring in situ and in real time. The high speed CCD camera opens up the possibility to observe the dynamics of the domains during poling and to probe the samples afterwards to evaluate the grating formed in the material. This monitoring method should be applicable to other ferroelectric crystals, as well.

Dynamics of green light-induced infrared absorption in KTiOPO4 and periodically poled KTiOPO4

Induced thermal-lens spectroscopy with a common-path interferometer has been used for high-sensitivity measurements of green-light induced absorption dynamics in single-domain and periodically pole ...

Single-longitudinal-mode Nd-laser with a Bragg-grating Fabry-Perot cavity

We demonstrate 0.85 W of power in a single longitudinal mode at 1066 nm from a Nd:GdVO(4) laser. The laser consists of only two components, the gain medium and a volume Bragg grating in glass, in a simple linear cavity comprising a combination of a Fabry-Perot cavity and a narrowband filter. Thanks to the narrowband Bragg grating, the single longitudinal mode is maintained for a cavity length up to 8 mm, while a continuous tuning of 25 GHz is achieved for a shorter cavity and lower power.

ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 μm source

A tandem optical parametric oscillator (OPO) is used to convert radiation from 1.064 microm to the mid-infrared. Spectral bandwidth narrowing close to 80 times compared with a conventional cavity was achieved by using a bulk Bragg grating as an outcoupler in a near-degenerate periodically poled KTiOPO(4) OPO. The narrowed 2,008 nm radiation was subsequently used for pumping the ZnGeP(2) OPO, which was tunable between 3.3 and 5.2 microm. Pulse energies of 170 microJ and pump depletion close to 70% were obtained in the ZnGeP(2) OPO. To our knowledge this is the first time the output from a near-degenerate type I PPKTP OPO has been used for ZnGeP(2) OPO pumping.

Tunable single-longitudinal-mode ErYb:glass laser locked by a bulk glass Bragg grating.

A single-longitudinal-mode ErYb:glass laser with a linewidth of 90 kHz is demonstrated by locking the laser wavelength to 1552.6 nm with a bulk glass Bragg grating. Using a piezoelectric actuator, the wavelength could be tuned over a range of 0.25 nm (31 GHz) in steps of 17 pm (2.1 GHz), with an output power of a few milliwatts.

Diode-pumped Er–Yb:glass laser passively Q switched by use of Co 2+ :MgAl 2 O 4 as a saturable absorber

We report on passively Q-switched operation of a diode-pumped Er-Yb:glass laser with a Co(2+):MgAl(2)O(4) plate as a saturable absorber. Optical pulses with peak power exceeding 2 kW and a pulse length of 2.3 ns have been generated. Single-longitudinal-mode Q-switched operation at 1.53 mum has been obtained by use of the Co(2+):MgAl(2)O(4) plate as an intracavity etalon. A discussion of the optimal Er(3+) concentration as well as optimization of the cavity design is included.

Efficient Nd:YAG Laser Frequency Doubling with Periodically Poled KTP.

Periodically poled flux-grown KTiOPO(4) was used for efficient extracavity 1064-nm Nd:YAG laser frequency doubling. A conversion efficiency exceeding 65% was obtained in Q-switched operation, and 1.34 W of average frequency-doubled power was generated with 2.2 W of mode-locked laser output. The conversion efficiency is approximately two times higher for periodically poled KTP than for conventional type II phase-matched KTP. The measurements indicate that periodically poled KTP is less susceptible to optical damage than type II KTP.

Backward quasi-phase-matched second-harmonic generation in submicrometer periodically poled flux-grown KTiOPO4

A 1 turn thick flux-grown KTiOPO4 sample was poled with a 720 nm domain period by employing deep-UV laser lithography, chemical patterning, and electric field poling. An atomic force microscope was ...