Yuji Oki

Multiwavelength distributed-feedback dye laser array and its application to spectroscopy

A multiwavelength, multistripe tunable laser array is proposed, and its application to absorption spectroscopy is demonstrated. Laser waveguides doped with Rhodamine 6 G dye were integrated on a plastic chip, and simultaneous output at different wavelengths was obtained by use of a distributed-feedback technique. A very low threshold of 3 muJ was attained, and spectrally narrowed output (<0.1 nm) was obtained. A scheme for digital spectroscopy is also proposed based on this laser array, and absorption spectroscopy of sodium atoms without wavelength scanning is demonstrated by use of a sodium-vapor cell.

Wide-wavelength-range operation of a distributed-feedback dye laser with a plastic waveguide

A compact distributed-feedback (DFB) dye laser with a plastic waveguide was developed. The DFB operation was attained by the interference of two pumping beams from a frequency-doubled pulsed Nd:YAG laser, and a wavelength range between 560 nm and 994 nm was continuously covered. The dye chip can instantaneously exchanged in any spectrum region. The threshold energy was decreased to the order of 100 µJ with the waveguide configuration. The maximum life of the dye chip was 106 shots.

Fabrication of a distributed-feedback dye laser with a grating structure in its plastic waveguide

Two approaches of fabricating grating structures for waveguided plastic dye lasers are described and compared for lasing performance. Rhodamine6G-doped poly(methyl methacrylate) (PMMA) film on a PMMA substrate was used for the waveguide, and a distributed-feedback (DFB) laser operation with a single-propagation mode was demonstrated. The performances of both types of permanent grating structured DFB dye laser were better than those of a DFB dye laser on a plain waveguide with a dynamic grating formed by the interference of two pump beams. Wide tuning range is expected by use of a multistripe DFB laser with different grating pitches.

Long lifetime and high repetition rate operation from distributed feedback plastic waveguided dye lasers

Abstract Long lifetime and high repetition rate laser operation was demonstrated from laser-dye-doped waveguides with distributed feedback (DFB) structures. The waveguides were fabricated with a spin-coating and lithography techniques, and DFB structure was written by an ultraviolet holography technique. A compact frequency-doubled Nd:YAG microchip laser was used as a pumping source, and the laser output wavelength range of 575–945 nm was obtained from 10 different kinds of laser-dye-doped plastic film and the laser performance was evaluated about 5 of them. Very low pumping energy requirement of around several μJ could extend the durabilities of the DFB dye-doped waveguides, and the lifetime of more than one million shots was obtained. Further a high repetition laser operation up to 1000 pps was demonstrated with an output energy stability of less than ±0.5%. A palm-top size tunable laser is realized by this configuration.

Waveguide dye laser including a SiO2 nanoparticle-dispersed random scattering active layer

We presented a dual-layered waveguide dye laser including a random active layer with nanoparticle doping. A slope efficiency of 12.0% and an energy threshold of 0.34μJ were obtained in a single-longitudinal-mode operation.

Electroluminescence from completely horizontally oriented dye molecules

A complete horizontal molecular orientation of a linear-shaped thermally activated delayed fluorescent guest emitter 2,6-bis(4-(10Hphenoxazin-10-yl)phenyl)benzo[1,2-d:5,4-d′] bis(oxazole) (cis-BOX2) was obtained in a glassy host matrix by vapor deposition. The orientational order of cis-BOX2 depended on the combination of deposition temperature and the type of host matrix. Complete horizontal orientation was obtained when a thin film with cis-BOX2 doped in a 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) host matrix was fabricated at 200 K. The ultimate orientation of guest molecules originates from not only the kinetic relaxation but also the kinetic stability of the deposited guest molecules on the film surface during film growth. Utilizing the ultimate orientation, a highly efficient organic light-emitting diode with the external quantum efficiency of 33.4 ± 2.0% was realized. The thermal stability of the horizontal orientation of cis-BOX2 was governed by the glass transition temperature (Tg) of the CBP ho...

Thin-Layer Ablation of Metals and Silicon by Femtosecond Laser Pulses for Application to Surface Analysis

For the purpose of thin-layer surface analysis, comparison of laser ablation by 24 ns ArF laser pulses at 193 nm and that by 150 fs Ti:sapphire laser pulses at 780 nm for samples ranging from metals to semiconductors is reported. In contrast to nanosecond laser pulses, the ablation threshold for femtosecond laser pulses could be reduced significantly. In particular, the threshold for a Si sample was reduced to about one order of magnitude, and an ablation rate of 0.48 nm/shot was obtained at 5% above the threshold fluence. The root-mean-square (RMS) growth rate in the roughness of the ablated surface was 0.05 nm/shot. These results show the advantages of femtosecond laser ablation for trace element analysis of a wide range of materials, coupled with laser-induced fluorescence (LIF) spectroscopy.

Highly photo-stable dye doped solid-state distributed-feedback (DFB) channeled waveguide lasers by a pen-drawing technique

Pyrromethene dyes doped polymeric channeled waveguide lasers with permanent DFB structures were fabricated via a novel pen-drawing technique with the patterned polydimethylsiloxane (PDMS) chips fabricated through a casting process as the substrates. With the high resolution dispensers, dye doped high viscosity pre-polymers were written into the PDMS grooves and the cross-section of the channeled waveguides could be controlled by both the polymer composition and the pen-drawing parameters. Highly stable laser output with 4.8 × 10(6) pulses of laser lifetime at 500 Hz of pump repetition rate has been obtained, which is suggested to be among one of the best results of pyrromethene 567 (PM567) up to date.

Tunable Ultrashort Pulse Generation from a Waveguided Laser with Premixed-Dye-Doped Plastic Film

A highly compact ultrashort pulse generator is proposed and demonstrated with a poly-methylmethacrylate (PMMA) waveguide doped with a mixture of laser dye (Rhodamine 6G) and saturable absorber (DODCI). A series of spikes with a pulse duration of 20–30 ps was generated by a distributed feedback dye laser pumped by a ns Nd:YAG laser. First, the spikes were shortened by passive Q-switching effect of the saturable absorber. Then they were compressed to 9 ps FWHM by passing a pulse compressor having an alternative chain of amplifier and saturable absorber integrated on the same waveguide. Performances of both devices were evaluated by calculation and confirmed experimentally.

Extremely sensitive Na detection in pure water by laser ablation atomic fluorescence spectroscopy

Abstract An extremely sensitive trace element detection technique in water is proposed and demonstrated, in which the excimer laser ablation is used to generate a densely atomized plume and the generated atoms are detected by sensitive laser-induced fluorescence (LIF) spectroscopy with a CW dye laser. Very strong LIF signal is detected without any interference of the plume radiation for 1 ppt, 10 μl Na water solution. A detection limit less than 0.1 ppt or 1 fg can be attained by this scheme.