Toru Tajime

208-W TEM00 operation of a diode-pumped Nd:YAG rod laser.

208-W average-power TEM(00) -mode operation from a diode-pumped Nd:YAG rod laser was demonstrated. The side-pumping method of generating a high-gain aberration-free rod, the bifocusing-compensation technique with two identically pumped rods, and a suitable choice of beam spot size were employed in the design of this laser. At the maximum pump power of 1.1 kW the fundamental transverse-mode operation (M(2)<1.1) was characterized by 7.6% electrical efficiency. The extraction efficiency was almost 60% of full multimode operation. Stable operation was obtained within a pump-power range of 15% of the maximum pump power.

An electroabsorption modulator module for digital and analog applications

This paper presents an electroabsorption modulator (EAM) module for digital and analog (D/A) applications. Optically broad-band operation of the EAM module is studied for such digital application as wavelength division multiplexing (WDM) systems. Utilizing anisotropic electroabsorption of a multiple quantum-well (MQW) EAM, 40- and 100-nm bandwidth operations in 2.5-Gb/s digital signal transmission over 200-km standard fiber are confirmed by the experiments and the simulations, respectively. For analog applications, low distortion and high link gain characteristics of the EAM module are investigated at the wavelength of 1535 nm. High spurious-free dynamic range of 123 dB/spl middot/Hz/sup 4/5/ and high link gains of -10.3 dB with matching circuit and -20.6 dB without matching circuit are obtained using the EAM module.

Multilens system design with an athermal chart

We have introduced an athermal chart that plots chromatic dispersive power and thermal dispersive power on a Cartesian coordinate, and we give the design method of a multilens system in contact that satisfies achromatism and athermalization. The advantages of this chart are (1) that the condition of achromatism and athermalization is clear and (2) that the approximate power of the lenses that compose the multilens system is easily found on the chart. Design indices are given through a few design examples with an athermal chart.

Improved pump-beam distribution in a diode side-pumped solid-state laser with a highly diffuse, cross-axis beam delivery system

A new cavity for diode side-pumped solid-state lasers was designed, built, and tested. The results were efficient absorption of pumped light in the media and homogeneous pumped-beam distribution under various pump-power levels, which generated Nd:YAG active media of different radii and concentrations and shifts of the diode wavelength. Full-multimode quasi-continuous pump operation with a slope efficiency of 40.5% was obtained from a plane-plane resonator equipped with two Nd:YAG rods. At a maximum average pump power of 1.33 kW, the optical-to-optical efficiency was 31.4%. Single-transverse-mode operation (M(2) factor of less than 1.1) of 163 W was demonstrated.

100-W class diode-pumped Nd:YAG MOPA system with a double-stage relay-optics scheme

Abstract We describe a diode-pumped master-oscillator power-amplifier system with two-rod Nd:YAG media and double-stage relay optics scheme. At the repetition rate of 2.4 kHz it delivers an average power of 108 W with Q-switched pulses of 47 ns duration. The laser beam is characterized by an M 2 factor of 2.5×2.7. A model of amplification, which takes into account the temporal overlap between the beams that propagate forwards and backwards in the amplifier stage, was developed to explain the experimental results.

Absorption characteristics of the γ-0 bandof nitric oxide

The absorption by the gamma-0 band of nitric oxide at 2260 A has been studied. Its apparent absorption cross section depends both on total pressure and its concentration. In order to investigate these absorption characteristics quantitatively, a line by line analysis was made. Good agreement was obtained between the experimental and computed results of the absorption cross section.

All-solid-state high-power conduction-cooled Nd:YLF rod laser

A high-average-power conduction-cooled diode-pumped Nd:YLF rod laser has been developed. A new conduction-cooled side-pumping scheme with a solid prismatic pump-light confinement cavity was employed. A transparent, high-thermal-conductivity MgF>(2) prism was used as a highly efficient pump cavity as well as a low-thermal-resistance heat spreader. The pumping efficiency and thermal resistance of the cavity were 85% and 0.20 degrees C degrees W, respectively. When this scheme was combined with heat pipes for heat removal, a maximum average output power of 72 W was demonstrated, with an optical slope efficiency as high as 49%.

Dual-band optical systems with a projective athermal chart: design

We introduce a projective athermal chart that is produced as a view plane of the perspective projection of a three-dimensional space consisting of two chromatic dispersive powers and the mean thermal dispersive power. In addition, we show a design method for dual-band optical systems with this chart and a design example of a three-lens optical system operating in the 3-5- and 8-12-mum wavelength bands.

Rosette Scan Infrared Sensor

This paper describes the design analysis and results of performance test of a rosette scan infrared sensor which can be used as a thermal imager as well as a radiation seeker for search and tracking. The fundamental properties of a sensor are discussed, and the relationship between sensor parameters has been made clear. The effect of bandwidth on the noise equivalent irradiance(NEI) is also investigated by using a simplified model. On the basis of these analyses, the sensor which responds in the 3 to 5 μm spectral band has been designed, fabricated and tested. It has been verified that the minimum NEI over the total field of view could be realized by optimizing the bandwidth at the center of the field of view. The ability as a thermal imager has also been demonstrated by displaying rosette-scanned thermal images on a CRT monitor, and the detection capability of a target on a display has been evaluated by measuring the minimum detectable temperature difference(MDTD).

New design method for athermalized optical systems

This paper describes a new design method for athermalized optical systems. It can be accomplished by combining optical materials and by selecting suitable lens powers. However, there are difficulties in determining material and power of each lens, because achromatism is simultaneously required. To determine the condition of eliminate thermal focus shift and longitudinal chromatic aberration easily by simple drawing, an athermal chart is proposed which is constructed by plotting chromatic dispersive power and thermal dispersive power on a cartesian coordinate system.