Chao Ye

Narrow linewidth operation of solid state dye laser based on sol–gel silica

Abstract Narrow linewidth laser action was achieved in dye-doped sol–gel derived silica slabs. Using a double grating resonator cavity, one grating serving as the beam expander and the other for tuning, laser output with linewidth as narrow as 3.3 GHz was realized for dye-doped sol–gel silica slabs. The output wavelengths were 560 nm, 474 nm and 378 nm respectively for rhodamine 6G-, Coumarin 460-, Exalite 377-doped samples. Oscillatory laser waveform indicative of two or three longitudinal mode lasing was also observed.

Output performance of a dye‐doped sol‐gel silica laser in the near UV

Visibly transparent near‐UV dye (Exalite 377E)‐doped silica in the form of parallelepiped were prepared by the low‐temperature sol‐gel process. The laser output performance of dye‐doped sol‐gel silica samples pumped by a short pulse (1 ns) N2 laser at 337 nm was reported. With a grating as the wavelength selection element, the laser was tuned from 367 to 387 nm with a laser linewidth of 2 nm. Using a resonator cavity consisting of two flat mirrors, the sol‐gel laser showed a slope efficiency of 34.7% and a pump energy threshold of 20 μJ. The variation of sol‐gel laser energy output as a function of the number of pulses under repetitive N2 laser excitation was investigated. The laser output energy decreased initially with the number of shots. The output energy recovered to its original intensity after a ten minute interruption in pumping. In this way, the dye‐doped samples showed no signs of long term degradation after being irradiated at 337 nm for tens of thousand shots.

Simultaneous generation of multiple pairs of transverse electric and transverse magnetic output modes from titania zirconia organically modified silicate distributed feedback waveguide lasers

Output polarization and output wavelength of titania zirconia organically modified silicate distributed feedback waveguide lasers were found to be dependent on the polarization of the crossing pump beams. Output waves with transverse electric polarization were obtained when the pump beams were s-polarized. Transverse electric and transverse magnetic optical waves belonging to the same propagation mode were generated by crossing two circularly polarized or p-polarized pump beams. Tuning of the polarized laser output was also achieved by varying the crossing angle. Up to sixteen output wavelengths corresponding to eight pairs of polarized output from eight propagation modes were observed simultaneously for a planar waveguide with a thickness of 6.7 μm.

Distributed feedback sol-gel zirconia waveguide lasers based on surface relief gratings

Distributed feedback waveguide lasers based on dye-doped sol-gel zirconia films with permanent grating structures were demonstrated. The permanent grating was realized by employing a novel epoxy-based azo-polymer that generates a surface relief grating by a photo-isomerization process induced by two interfering writing beams. When employing the rhodamine 6G dye, tuning of the output wavelength of the distributed feedback waveguide laser from around 575 nm to 610 nm can be achieved by adjusting the tilting angle between the orientation of the grating and the pump beam.

Near infrared distributed feedback lasers based on LDS dye-doped zirconia-organically modified silicate channel waveguides

LDS dyes were doped into zirconia-organically modified silicate (ORMOSIL) materials prepared by low temperature sol-gel technique. Embedded channel waveguides were fabricated using wet etching of glass substrates followed by deposition of the LDS 925-doped zirconia-ORMOSIL in the channel. Near infrared distributed feedback (DFB) laser action was induced in the LDS 925-doped sol-gel channel waveguide. Narrow line-width (<0.5 nm) tuning of the output wavelength was achieved by varying the period of the gain modulation generated by a nanosecond neodymium:YAG laser at 532 nm. Tuning range was from 787 nm to 933 nm. The dispersion behavior of the laser output was checked by comparing experiments with the predictions of Marcatilis theory. Additionally, near infrared (NIR) wide-band tuning and high-order DFB lasing operation were realized in LDS dye-doped planar waveguides.

Distributed feedback sol-gel zirconia channel waveguide lasers

We fabricated dye-doped zirconia channel waveguides using wet or dry etching of quartz substrates followed by sol-gel deposition of the Rhodamine 6G-doped zirconia in the channel. Distributed feedback laser action was generated in the channel waveguides by crossing two nanosecond laser beams at 532nm. Maintaining the depth of the active zirconia layer at 3μm, narrow linewidth lasing was achieved for rectangular channel waveguides with widths at 5, 6.5, and 10μm. Wavelength tuning was achieved from 570to608nm. The output laser mode was identified as the fundamental E11x mode. The dispersion behavior of the laser output was checked by comparing experiments with the predictions of Marcatili’s theory.

Wavelength tunable two-photon-pumped distributed feedback zirconia waveguide lasers

Two-photon-pumped distributed feedback laser action of narrow linewidth output was demonstrated in zirconia waveguides doped with trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium p-toluene sulfonate, a compound showing strong two-photon upconverted emission around 620 nm. Transient gratings were generated in the waveguides by crossing two nanosecond 1.06 µm beams. Operated at the third-order Bragg resonance condition, tunable narrow linewidth laser emission was observed from 618 to 640 nm by varying the intersection angle of the crossing beams around 61°. Tunable lasing at the second-order Bragg condition was also obtained when the zirconia waveguides were pumped at 532 nm.

Thermally tunable multiwavelength output waveguide laser source of Zirconia-Titania-ORMOSIL thin films

Organic laser dye doped Zirconia-Titania-ORMOSIL waveguide thin films with refractive index from 1.55 to 1.59 were prepared by the sol-gel method. The thickness can be varied from 0.97 μm to 10 μm by changing coating speed. Distributed feedback waveguide lasing with multi-wavelength were observed with a periodic gain modulation induced by a frequency-doubled Nd:Yttritium-aluminum-garnet (YAG) laser. Wavelength tuning typically from 597 nm to 602 nm was demonstrated in Rhodamine 6G doped multiple mode waveguiding ZrO2-TiO2-ORMOSIL thin films DFB configuration by varying the temperature from 20°C to 120°C. The thermal coefficients of DFB waveguide laser wavelength and the refractive index of the film were deduced. This compact DFB laser device can be applied to measure the thermal coefficients of refractive index of the active films, and used as a remote temperature sensor.