Highly efficient blue-light generation from a compact, diode-pumped femtosecond laser by use of a periodically poled KTP waveguide crystal

Terahertz optical properties of potassium titanyl phosphate crystals

This paper studies the terahertz optical properties of nonlinear potassium titanyl phosphate crystals with different conductivities in the spectral range of 0.2 to 2.6 THz. The observed properties are characterized by several absorption lines lying along different optical axes which represent the relevant potassium sublattice phonon modes. The peculiarities of these absorption lines are attributed to the structural order of potassium ions.

Low-cost, broadly tunable (375-433 nm & 746-887 nm) Cr:LiCAF laser pumped by one single-spatial-mode diode

We describe a low-cost, compact, and efficient Cr(3+):LiCaAlF(6) (Cr:LiCAF) laser that is broadly tunable in the near infrared (746-887 nm) and blue/ultraviolet (375-433 nm) regions of the optical spectrum. The pump source is a 660 nm single-mode-diode with 145 mW of output power. A melt-grown Cr:LiCAF crystal with an extremely high figure of merit above 2000 was used as the gain medium. This enabled the construction of a high-Q-cavity with continuous wave (cw) lasing thresholds as low as 3 mW, slope efficiencies as high as 54%, and output powers up to 63 mW. The stored intracavity power levels were above 30 W. By placing a beta-barium-borate crystal at a second intracavity focus, we could obtain tunable cw blue/ultraviolet radiation with output powers up to 3.5 mW around 400 nm. When mode-locked using a saturable Bragg reflector around 800 nm, the Cr:LiCAF laser produced 95 fs pulses with average powers of 33 mW and peak powers of 3.58 kW at a repetition rate of 85.5 MHz. Extracavity second harmonic generation enables generation of femtosecond pulses around 400 nm. These results demonstrate the possibility to grow Cr:LiCAF crystals with passive losses below 0.15% per cm, which enables construction of low-cost and complexity systems that are pumped only with one low-power single-mode-diode.

Theoretical modeling and experiment of refractive index change in He+ ion-implanted KTP waveguide

A theoretical model is presented to explain the refractive index change in the ion-implanted KTP waveguide, which includes respective contributions of spontaneous polarization, molar polarization and molar volume, and photoelastic effect. Numerical calculations of refractive indices along different crystalline orientations (X, Y, and Z) as a function of the lattice damage level, determined by Rutherford back-scattering/channeling technique, are performed based on the results from a set of z-cut KTP crystals implanted by 300 keV He+ ions in doses ranging from 4×10(16) to 8×10(16) ions/cm2. The theoretical results show consistency with the experimental data. To our knowledge, this is the first model to comprehensively describe the ion-implanted KTP planar waveguide.

Efficient green-light generation by frequency doubling of a picosecond all-fiber ytterbium-doped fiber amplifier in PPKTP waveguide inscribed by femtosecond laser direct writing

We have demonstrated an ultrashort, compact green light radiation by frequency doubling of an all-fiber ytterbium-doped fiber laser source in a PPKTP waveguide fabricated by femtosecond laser pulses. Using the fabricated PPKTP waveguide crystal containing a 10 mm single grating with a period of 9.0 μm, we generate 310 mW of picosecond radiation at 532 nm for a fundamental power of 1.6W, corresponding to a conversion efficiency of 19.3%. The temperature tuning range of 8°C is achieved for a fixed fundamental wavelength of 1064 nm, the FWHM of the wavelength tuning curve is 4.2 nm at room temperature. The generated ultrashort pulses at 532 nm are of great importance and have comprehensive applications in photobiology research and high-resolution spectroscopy.

Planar-waveguide quasi-phase-matched second-harmonic-generation device in Y-cut MgO-doped LiNbO3

We designed a planar-waveguide quasi-phase-matched second-harmonic-generation device, which consists of a Y-cut periodically poled 5 mol.% MgO-doped LiNbO3 core and SiO2 claddings, that provided a 1.08 W green light with 30% conversion efficiency by using a 7 mm long sample at room temperature. The highest conversion efficiency of 49% at 0.88 W second-harmonic generation was attained by using an 18 mm long device.

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W(-1) cm(-2) efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.

Compact continuous-wave blue lasers by direct frequency doubling of laser diodes with periodically poled lithium niobate waveguide crystals

A compact continuous-wave blue laser has been demonstrated by direct frequency doubling of a laser diode with a periodically poled lithium niobate (PPLN) waveguide crystal. The optimum PPLN temperature is near 28 degrees C, and the dependence of waveguide crystals on crystal temperature is less sensitive than that of bulk crystals. A total of 14.8 mW of 488-nm laser power has been achieved.