Direction Characteristics of an Optically Pumped Far Infrared Ring Laser Emission

Direction characteristics of emission have been observed on an optically pumped far-infrared (FIR) ring laser. The FIR output from a CH3OH laser is emitted in only a direction depending on the tuning of the FIR cavity. This phenomenon is analyzed theoretically by a 3-level laser model supported by a well-known 2-mode laser theory. The model explains the directionality of the FIR output for significant pump detunings and for small pump powers. The model also predicts that bidirectional emission occurs for large pump powers or for small detunings of the pump transition

Optical Measurement of Cooling Rate During Splat Coolling Process

Optical Measurement was examined to measure the cooling rate of the thin ribbon produced by splat cooling of single roller. The temperature measurements of metal surface were made by the surface radiance in the range of IR wave length, and high speed PIN Si photodiode was used to measure the radiance. The cooling rate (V) of the thin sample is proportional to the rotational speed (R) over a range from 500 to 4000 rpm, and it is V = 2.42 × 102R in Fe-C-P system alloy and is V = 2.20 x 102R in Fe-Ni-B system alloy. The critical cooling rate of amorphous ribbon is about 2.1 × 105∼2.4 × 105 K/s in Fe-C-P system alloy and is about 8.3 × 105∼8.4 × 105 K/s in Fe-Ni-B system alooy, and those critical cooling rates change the value depending on the composition of the alloy. This optical measurement may be very useful to determine the cooling rate of the sample moving at high speed, by non-contact measurement