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We succeeded in observing the continuously tunable, pulsed InSb SFR (Spin-Flip Raman) laser emission in the infrared region of 11∼16µm (11.4∼16.3µm) from only one InSb device, merely by adjusting the pumping wavelength (11 lines from the infrared NH3 laser) and the applied magnetic field (0∼80 kGauss).

By replacing the conventional (non line-selective) unstable resonator, we succeeded in developing the very high power line-selective (line-tunable) CO2 laser as a pumping source for high power molecular gas (e.g.NH3) lasers in the infrared and far-infrared regions.

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In this paper, infrared (IR) and far-infrared (FIR) laser emissions from a TE CO 2 laser pumped NH 3 gas are reported. 8 IR laser emissions near the wavelength of 12 μm were observed by using 4 different CO 2 laser lines for the pumping. 3 IR laser emissions in P-branch of vibrational-rotational band (ν 2 → G) oscillated simultaneously in two pumping cases, i.e. pumping with the R(30) or R(16) line of 9.4 μm band from the CO 2 laser. 26 FIR laser emissions (26.45 μm ∼ 281.0 μm) were observed by using 12 different CO 2 laser lines, and the 10 FIR emissions of them may be new laser emissions as far as we know.

The characteristics of NH3 laser pumped by a TE CO2 laser pumped NH3 laser is discussed. 38 IR laser lines in the wavelength region from 10.7 to 13.3μm wser observed by CO2, 9R (30) line. The emission intensity of each line depended on both the temperature of the NH3 laser tube and the ratio of NH3 to N2. Most of the laser lines could, however, be observed under a same condition. 12.280μm line was observed for the pumping of CO2, 9R (30) and CO2, 10P (32) lines respectively. The slight frequency difference in both cases were discsuued. Furthermore, 12.078μm line, which was the strongest emission line in this experiment, was used to pump an InSb spin-flip Raman (SFR) laser, successfully.

The magnetic tuning characteristics of InSb laser pumped by a TE CO2. laser were studied.The tuning characteristic depended on the carrier density of n-InSb sample. For a sample with low carrier density, the emission energy shifted monotonously to higher energy with increasingmagnetic field and only one linear shift varying as Δe=(\hbarωc-|gc|βH)/2 was o bserved at a high magnetic field. For a sample with high carrier density, the emission energy shifted to lower energy at a low magnetic field, and at a high magnetic field two linear shifts with differentrates to higher energy varying as Δe=(\hbarωc±|gc|βH)/2 were observed. The polarization and the intensity of emission were also investigated. The zero-field emission energy was measured for samples with different carrier densities. A simple transition model is proposed, which can explain the observed magnetic tuning characteristics.

A study of pulsed InSb spin-flip Raman laser, using TE CO and CO2 lasers as pumping sources, is reported. Pumping wavelength dependences of magnetic tuning and output power were investigated, and magnetic tuning characteristics were also studied for the samples with different carrier densities. Effective g-factor of conduction electron in InSb was estimated from the measured frequency shift. Furthermore, absorption spectra of NO gas were observed with this pulsed spin-flip Raman laser.

A far-infrared (FIR) NH3 laser was resonantly pumped with a line-tunable infrared (IR) NH3 laser. The number of the observed FIR laser lines amounted to 33. Most of them belonged toaR(J,K) rotation-inversion transition in (0, 1, 0, 0) vibrational state. The line tunability of sealed-off FIR NH3 laser was almost achieved in 90, 115, 150, and 220 μm wavelength regions by the selective line tuning of the pumping IR NH3 laser.

Laser emission in InSb resonantly pumped by a TE CO laser was observed, and the magnetic tuning characteristic was investigated for the samples with different carrier densities. The tuning range of about 8 meV (65 cm-1) was obtained for magnetic fields of up to about 20 kG.

The onset of current oscillation in a germanium slice in a transverse magnetic field was studied by taking into consideration the existence of gradient of carrier density along the direction of thickness. The gradient was estimated from the observations of 9.3 Gc microwave reflection and the threshold gradient experimentally determined for the onset of the density wave instability was compared with the theoretically estimated one. The results show that this threshold gradient is nearly equal to that of the instability of fundamental mode. However, the oscillation was quenched in a high transverse magnetic field.

Enhanced carrier diffusion associated with the density wave instability due to the gradient of carrier density in germanium slice was estimated at 77°K from the observations of (1) the distribution of carrier density along the direction of the thickness of the slice in the transverse magnetic field and (2) the transient time necessary for the decrease of the gradient of carrier density. The results show that when the instability occurs, the ambipolar diffusion constant D a of hot carriers becomes very large, i.e., D a ∼105 cm2/sec (at 700 V/cm) which is larger about an order of magnitude than that before the instability occurs. The phenomenon is discussed in conjunction with the current oscillation (wherein microwave emission was also observed) in germanium slice, as well as the frequency response of the devices relative to the magnetic barrier layer effect.

It is shown that the electric field intensity (E t h ) necessary for observing the effective carrier injection into long and thin germanium slice increases with the increasing transverse magnetic field intensity, even when lifetime of carriers in the slice becomes longer with the transverse magnetic field. The phenomenon is considered by the concept of the field-driven, volume-controlled and space charge limited current in long specimens of semiconductors presented by Lampert and Rose in conjunction with the transverse magnetic field effect. The calculated values of the threshold electric field intensity in transverse magnetic field are compared with the experimental results of N-type ana P-type materials with different dimensions at 77°K. It is suggested that the phenomenon will be influenced, though indirectly, by the space charge due to the Hall effect.