CW Oscillation Research Articles

Infrared Speetroscapy by Pb Sn Te Diode Lasers

Cw oscillation of Pb1-xSnxTe diode lasers at 77° K was achieved. The lasers are double hetero-structured, and were fabricated by liquid phaseepitaxial method. The life of the laser was more than 3000hrs. Using these lasers, infrared spectra of C2H6, SO2, NH3 and SF6 were observed.

Cw and improved pulsed operation of the 14- and 16-μm CO2 lasers

The performance of the 14- and 16-μm CO2 lasers produced in the electric discharge gasdynamic laser has been significantly improved by the addition of a small percentage of H2 to deactivate the (0110) level. This addition tripled the pulsed output of the laser, and 45 μJ at 14 μm and 25 μJ at 16 μm were observed. cw oscillation was achieved for the first time, with output powers of 0.6 and 0.9 W, respectively. The effect of collisional processes in limiting the CO2 density is discussed.

Frequency-locking of a CW dye laser to the center of the sodium D lines by a Faraday filter

Single-mode CW oscillations at the center of the sodium D lines have been achieved by inserting a Faraday filter in an argon-laser-pumped dye laser cavity. The oscillations at the D 1 and D 2 lines can be selected by choosing adequate values of the sodium temperature and the magnetic field strength. Experimentally obtained conditions to get the single-mode oscillations at the center of the D lines are compared with the theoretically calculated feature of the Faraday filter, and a relatively good agreement has been found. The shifts of oscillation frequencies due to the magnetic field are also discussed.

Embedded-stripe GaAs-GaAlAs double-heterostructure lasers with polycrystalline GaAsP layers - I: Lasers with cleaved mirrors

We report a new type of embedded stripe laser in which low-order mode CW oscillation is successfully attained at room temperature. In order to achieve lateral current confinement, a high-resistivity polycrystalline GaAsP layer is formed around the mesa stripe by selective vapor-phase growth technology. It turns out that a stable single-mode operation is attained at an injected current up to several times the threshold value.

Embedded-stripe GaAs-GaAlAs double-heterostructure lasers with polycrystalline GaAsP layers - II: Lasers with etched mirrors

We report a new type of embedded stripe laser in which low-order mode CW oscillation is successfully attained at room temperature. In order to achieve lateral current confinement, a high-resistivity polycrystalline GaAsP layer is formed around the mesa stripe by selective vapor-phase growth technology. It turns out that a stable single-mode operation is attained at an injected current up to several times the threshold value.

Multilayered ion-implanted BARITT diodes with improved efficiency

Based on the model suggested in an accompanying paper[1], diodes having the multilayered n + ipvn + structure have been fabricated from silicon material using ion implantation techniques. Systematic descriptions of their fabrication and evaluation are presented. Microwave CW oscillations at C-band (∼7.5 Ghz) have been observed in some of our devices. The measured maximum power output was in the range of 40 mw and the efficiency was ∼5%. The obtained efficiency is the best reported for any BARITT diode. This result indicatest hat the retarding field region in BARITT diodes may be used advantageously to provide a favorable phase delay between the injected current and the a.c. voltage and leads to improved efficiency BARITT oscillators.

200-GHz 50-mW CW Oscillation with Silicon SDR IMPATT (Short Papers)

Silicoin SDR IMPATT diodes have been operated continuously in 200- and 300-GHz bands. A p+-n junction structure was formed by thermal diffusion of boron and ion implantation of phosphorus ions. CW output power of 50 mW was obtained at 202 GHz with 1.3-percent conversion efficiency. At 301-GHz CW output power of 1.2 MW was observed.

Simultaneous cw laser oscillation on transitions of Cd + and I + in a hollow-cathode He-CdI 2 discharge

Continuous-wave laser oscillation has been obtained on four transitions of Cd + and eleven transitions of I + using a hollow-cathode He-CdI 2 discharge as active medium. Laser output characteristics are similar for both Cd + and I + transitions, and simultaneous cw oscillation has been achieved at wavelengths ranging from blue (4416 Å Cd +) through green ( 5337 5378 Å Cd +, 5407 Å I +), yellow ( 5678 5761 Å I +) and orange (6127 Å I +) to red (6585 Å I +).

Laser emission from polished NdP5O14 crystals with directly applied mirrors

We report on crystal processing, laser fabrication, emission spectra and output characteristics of neodymium pentaphosphate lasers. We obtained cw oscillation with an output power of 19 mW from a crystal with dielectric mirrors directly applied on polished (001) planes. We pumped longitudinally with 280 mW of an argon ion laser at 514 nm focussed to a 94-μm diameter. Near threshold our laser operated in the vicinity of 1053 nm; when pumped 1.6 times threshold it operated dominantly in the vicinity of 1063 nm.

Cw chemical transfer CO2 laser

The combustion of Mg vapor in N2O with He and Co2 diluents in a low-loss coaxial laser cavity has resulted in cw oscillation at 10.6 μm. The performance characteristics of the flame laser in a coaxial geometry were found to differ significantly from those expected on the basis of previous gain measurements taken in a transverse flow configuration.

Continuous oscillation of a lithium neodymium tetraphosphate laser with 200-µW pump threshold

Room temperature CW oscillation of a lithium neodymium tetraphosphate (LiNdP <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> ) (LNP) laser with thresholds in the fractional milliwatt range is reported. With a 5145-Å pump, observed threshold was 200 μW and the slope efficiency was 43 percent.

Improved efficiency microwave BARITT oscillators by delayed injection

A new microwave BARITT diode structure which utilizes an intentionally added retarding-field region is presented. By taking advantage of the carrier diffusion at low velocities in this region, the injected current is delayed relative to the ac voltage and improved efficiency diodes are obtained. Microwave CW oscillation at C band with efficiency of ∼4 percent has been realized. Although the efficiency is improved over previous BARITT diodes, it is believed that considerable further improvements are possible by further optimization.

CW oscillation characteristics of GaAs Schottky-barrier gate field-effect transistors

The CW oscillation characteristics of GaAs Schottky-barrier gate FET's have been examined at 10 GHz. The maximum output power of 41.2 mW and the maximum efficiency of 15.6 percent have been obtained for the GaAs FET with a gate length of 1.5 µm and an electrode width of 300 µm. The experimental results have shown that the GaAs FET possesses promising features for an oscillator application as well as an amplifier application.

Single longitudinal mode operation of cw junction lasers by frequency-selective optical feedback

cw oscillation in a single longitudinal mode is reported for stripe-geometry junction lasers operated at room temperature with frequency-selective optical feedback. The frequency-selective feedback, obtained by optically coupling a diffraction grating to the diode, is used to select a single mode of the normally multimode spectrum generated by the diode laser itself. Single-frequency oscillation is observed for currents up to 30% above threshold. The oscillation frequency has a linewidth determined primarily by the internal dynamics of the diode and is tunable over the entire multimode spectrum. Additional experimental results demonstrate the homogeneous broadening of the radiative line in these lasers.

CW high-pressure tunable CO&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;laser with a mixture of CO&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;isotopes

The qualitative theory of the CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> laser at atmospheric pressure was developed. Investigations of a CW CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> laser at high pressure with conventional and waveguide resonators and obtaining CW oscillation in the mixture of three isotopic molecules, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> O <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> O, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , are reported. The problem of building a super-high-resolution spectrometer on the basis of a CW high-pressure CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> laser with mixed isotopes is discussed.

Continuous oscillation of a (Sc, Nd) pentaphosphate laser with 4 milliwatts pump threshold

We report on room temperature cw oscillation of a scandium neodymium pentaphosphate (Sc: NdP5O14) laser pumped with an argon laser. The threshold pump power is, to our knowledge, the lowest obtained so far at room temperature with any laser material.

NdLa pentaphosphate laser performance

Laser operation is reported in a new crystalline material with high Nd content (2 × 1021 cm−3) whose concentration quenching is smaller than in other hosts. This material, NdLa pentaphosphate (Nd0.5La0.5P5O14) in the form of a 35-μm-thick crystal platelet was pumped with a pulsed Rhodamine 6G dye laser. The oscillation threshold with feedback from the uncoated surfaces was [inverted lazy s] 20 μJ of absorbed pump light. This indicates an optical gain coefficient of [inverted lazy s] 800 cm−1 corresponding to an excitation of more than half of the Nd ions in the material. This high gain resulted in a compression of the cavity mode spacing by a factor of 14. Using external mirrors, cw oscillation with a threshold of 25 mW absorbed power of an argon laser was achieved with a 1.4-mm-thick crystal. Measured parameters of the lasers are in good agreement with theory.

A survey of CW and pulsed Gunn oscillators by computer simulation

A computer simulation survey has been carried out on X-band CW and pulsed Gunn oscillators with a variety of contact conditions. It is shown that devices with a large cathode doping notch will have a nearly constant bias voltage-frequency product for optimum RF power generation. Such a relationship is not clear for devices with a smaller notch that is large enough to cause optimum injection of dipolar space charge. For both types of device there is an optimum ratio of transit frequency and cavity controlled frequency for optimum RF power generation. Several other detailed features of operation that cannot be explained by instantaneous-domain-formation models are dealt with, including the frequency dependence of the device conductance and capacity under conditions of optimum efficiency, and the bias current-voltage characteristics.

Temperature Stability of an MIC Gunn-Effect Oscillator (Short Papers)

A technique to temperature stabilize a Gunn-effect CW oscillator (C band) in microstrip, has been developed.

Theoretical and experimental study of GaAs IMPATT oscillator efficiency

This theoretical and experimental study was motivated by a specific need for a solid-state microwave generator with an output efficiency exceeding 20% and focused on the properties of GaAs avalanche transit-time devices. First, the dependence of the ionization rates and drift carrier velocities as a function of electric field and temperature is established. Then several methods of calculation, exact enough to take into account all the important efficiency-limiting effects in the device, are discussed and used to derive theoretical figures for the efficiency of a GaAs IMPATT oscillator, special attention being given to the influence of the doping profile. Finally, the experimental study is described, including device realization and experimentally measured efficiencies, and a comparison between these and the calculated values is done. It is shown that the best calculated performances can reach 30% efficiency and that it is possible to obtain experimentally cw oscillation efficiencies exceeding 20% with GaAs IMPATT devices having special types of doping profile.