Kazuo Fujisawa

Infrared multi-line NH3 laser and its application for pumping an InSb laser

Abstract In this paper, infrared (IR) emissions from a TE CO 2 laser pumped NH 3 laser are reported. 38 IR laser lines were obtained from a CO 2 9R(30) line pumped NH 3 : N 2 mixture by cooling a NH 3 laser tube, and 13 lines of them were new emission lines as far as we known. Four Q-branch lines were included and the others belonged to P-branch transitions. The 12.078 μm line, which was the strongest line in this experiment, was used to pump an InSb spin-fip Raman (SFR) laser which could be tuned from 13.35 to 13.55 μm.

Performances of Josephson Junction Harmonic Mixers with Harmonic Numbers 1–8 at 70 GHz

We have carried out a series of experiments at 70.03 GHz on Josephson junction harmonic mixers with harmonic numbers 1–8, using an identical Josephson junction. It was found that Josephson junction harmonic mixers operate differently depending on whether their harmonic numbers are odd or even. With odd-harmonic mixers, only finite-bias operation is possible, while with even-harmonic mixers, finite-bias and zero-bias operations are both possible. It is noted that a 2nd-harmonic mixer has a conversion efficiency equal to or higher than that of a fundamental mixer. The dependence of the conversion efficiency (η) on the harmonic number (N) was also studied, and the following approximate relations were determined: η~N-1.6 for finite-bias operation and η~N-1.4 for zero-bias operation.

Infrared and far-infrared laser emissions from a TE CO2 laser pumped NH3 gas

Abstract 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.

Emission Properties of Two-Photon Pumped InSb Laser under Magnetic Field

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.

Interfacial properties of Al2O3‐InP metal‐insulator‐semiconductor structure prepared in excess organophosphorus atmosphere

The effects of the excess phosphorus vapor added in the chemical vapor deposition (CVD) ambient on Al2O3‐InP metal‐insulator‐semiconductor (MIS) interfacial properties were investigated. The triethylphosphorus (TEP) was used as an excess phosphorus source gas suitable for the low temperature CVD. The change in the surface state density distribution (Nss) curves of the MIS diodes due to TEP introduction was clear: the Nss value of the broad peak at 1 eV, superimposed on the U‐shaped background, was reduced to one order of magnitude lower than that of the TEP‐free device.

The Laddertron—A new millimeter wave power oscillator

The Laddertron is a multi-gap klystron using ladders. This paper describes the theory and experimental results of the tube. Two types of Laddertrons are distinguished, namely the O -mode Laddertron and the π-mode Laddertron. The operation of each is analyzed and the equivalent circuit representations determined theoretically, whereby one can compute the resonant frequencies within an error of several per cent. A demountable experimental version of the π-mode Laddertron gave an output power of 10 watts for the 50-Gc band, an electronic tuning range of 300 Mc, and a mechanical tuning range of 2.5 Gc.

Resonant pumping far-infrared NH3 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.

Phenomenological Explanations for the Unbiased Operation of Even-Harmonic Josephson Junction Mixers

Even-harmonic JJ mixers allow unbiased operation, while odd-harmonic ones do not. Phenomenological explanations are presented for this phenomenon. Based on the voltage source model, a simple analysis is given that explains this phenomenon clearly. Furthermore, based on the current source model, this is studied by using a JJ simulator. In the odd-harmonic mixing, the waveform of supplied current has an odd symmetry, therefore, there is no mean junction voltage and no IF output. In the even-harmonic mixing, there is no such symmetry in the waveform of supplied current, therefore, there is a finite mean junction voltage and IF output.

Experimental Study of Josephson Junction 2nd-Harmonic Mixers at 70 GHz

Josephson junction (JJ) harmonic mixers with even-harmonic numbers can operate at zero bias voltage. Among them, low harmonic ones are expected to have a good conversion efficiency. Hence, we have done experiments on the 2nd-harmonic mixer at 70 GHz. It is found that mixing behaviors are classified into three types: zero-bias, finite-bias and intermediate operation. It is also found that the conversion efficiency of the 2nd-harmonic mixer is not so much less than that of the fundamental mixer. We obtained a conversion gain of +1.5 dB with the 2nd-harmonic mixer, and +2.0 dB with the fundamental mixer.

Low‐noise properties of unbiased even‐harmonic Josephson mixers

Noise properties of Josephson harmonic mixers were investigated both by simulation studies and by experiments. It was clarified that the unbiased mixing operation peculiar to even‐harmonic Josephson mixers has a lower noise temperature than the biased operation. A minimum noise temperature of 121 K was obained for an unbiased second‐harmonic Josephson mixer at 70 GHz. The cause of this low‐noise property of the unbiased mixing was attributed mainly to the nonexistence of noise down‐conversions by the odd‐harmonics of LO and the Josephson oscillation.