Use Of Laser Research Articles

Measurement of the spectral linewidth of semiconductor lasers for use with coherent optical communication systems

Semiconductor laser diodes with narrow linewidths (10 kHz–10 MHz) are essential for coherent fiber optical communication systems. Linewidth measurement techniques fall into three groups. We discuss each group and then focus our attention on the unbalanced interferometric method. We have developed, theoretically, the correlated unbalanced interferometric method and show that the envelope function of the beat signal is the Fourier transform of the original laser lineshape. We also propose novel approaches to the linewidth measurement techniques, such as serial use of two acoustooptic modulators for cross-correlation measurement and combination of Mach-Zehnder and Sagnac interferometers.

Excitation of rhenium atoms in a pulsed discharge

The authors describe an electrical discharge method and apparatus for the vaporization of rhenium and subsequent ionization of a rhenium-helium mixture for a metal vapor laser for use in a laser spectrometer. Data is given on the electron temperature and concentration and line widths and oscillator strengths of the ionized mixture for various discharge regimes.

High-power argon laser for use in holography

A cw stabilized ionic argon laser was constructed. The power of single-frequency radiation was 3 and 0.6W at wavelengths of 514 and 458 nm respectively. Active stabilization of the frequency ensured that the coherence length of the radiation was ~10 m.

Laser exposure timer

A hand-held unit has been constructed for routine measurement of exposure times of argon and krypton lasers. A small photodiode is used as the sensing element, and the measured exposure time in ms is observed on a liquid-crystal display. A series of measurements was made on a set of four lasers in use in ophthalmology departments in North Wales. Typically, the measured exposure times were observed to agree well with set values. Percentage errors were, however, often considerable at the shortest exposure settings. A small variation in values of exposure timings for a selected exposure time was found as a function of selected aiming-beam position. This presumably arises out of the design of the particular aiming-beam/shutter assembly. Although no serious shutter malfunction was detected, the ability to measure exposure times accurately was considered relevant to checking the delivered output of laser systems.

Lasers for use in medicine.

During the last quarter century the use of directed energy from lasers has become very important in medicine. Directed energy from lasers has been used to cut tissue, to cauterize bleeding, to drill small pressure relief holes and to selectively destroy tissue growths. In this paper lasers of interest in such applications are described and compared.

Development of sequence and regular band lasers for use as local oscillators in Thomson scattering alpha particle diagnostics (abstract)

Heterodyne detection will be used to measure the scattered signal from a 100-MW pulsed CO2 laser Thomson scattered from energetic alpha particles. This measurement requires local oscillators displaced from the pump line by 6 to 21 GHz. We are developing cw sequence and regular band N2O and CO2 lasers which provide many lines in the required frequency range. The sequence lines are obtained by using a small in-cavity hot cell. Operating characteristics will be discussed for a variety of experimental arrangements.

Lasers, their development, and applications at M.I.T. Lincoln Laboratory

A historical account of the work on lasers at MIT Lincoln Laboratory is presented. Highlighted are the efforts that led to the co-invention of the semiconductor laser and the Laboratory's later role in establishing the feasibility of GaInAsP/InP semiconductor lasers for use in fiber telecommunications at 1.3-1.5 \mu m wavelenths. Descriptions of other important developments include tunable lead-salt semiconductor and solid-state lasers for spectroscopy and LIDAR applications, respectively, as well as ultrastable CO 2 lasers for coherent infrared radar.

CO 2 laser stapedotomy: Is it practical?

The argon laser has been described as an instrument capable of performing stapedotomy for otosclerosis. Because of the possibility of cost ineffectiveness and damage to the saccule using the argon laser, this study was undertaken to ascertain the possibility of using the CO2 laser for stapedotomy. the operation was done on seven cats, and the resulting histopathologic findings were studied. Stapedotomy was also performed with the CO2 laser on human cadaver temporal bones to measure temperature changes in the vestibule and to develop guidelines for the laser's use in humans. The authors' results indicated that the CO2 laser can be used effectively and safely in cats and should be considered for human use.

Application of CO 2 lasers in mechanical engineering technology in the USSR

Lasers are finding many applications in mechanical engineering in the USSR. The various types of lasers in use are investigated and the main properties of laser welding and cutting are studied and compared with other forms of these processes. Methods of surface treatment and heat hardening are also investigated.

Reliability of 1.3-μm InGaAsP/InP laser diodes

Abstract Degradation mechanisms and methods for reliability improvement in 1.3–μm quaternary lasers for use in submarine fiber optic cable communications are reviewed. The reliable diode requires an optimized structure, such as a thin active layer and a narrow stripe width, to achieve a low threshold current Ith , high characteristic temperature To , and high maximum temperature for CW operation, T CW max. Accelerated long-term life test data predict an MTTF of ∼107 h at room temperature for state-of-the-art optimized lasers with To ∼ 80 K, T CW max ∼ 100°C, Ith ∼ 20 mA, and 5-mW optical power, which barely meets the system requirement. Based on the present rate of reliability improvement, a useful life of ∼109 h is forecast by 1986.

Criterion for improved linearity of 1.3-µm InGaAsP-InP buried-heterostructure lasers

Nonlinearities in tile light-current characteristics of planar-active buried-heterostructure (BH) lasers are associated with higher order mode transitions, spectral broadening and, in some cases, the onset of TM polarized stimulated emission. Measurements and calculations are presented which show that these nonlinearities appear at higher power in devices with reduced active volume. These results provide a practical guide to the fabrication of kink-free 1.3-μm InGaAsP buried-heterostructure lasers for use in high-bit-rate fiber communication systems.

Applications Of Semiconductor Lasers In Space Communications

Techniques for combining individual semiconductor lasers for use as a laser communication transmitter are discussed. The geometries, aging characteristics, and lifetimes of semiconductor lasers are reviewed, and the resulting effects on the laser communications transmitter are assessed.

Insulator Materials in High Power Lasers for Inertial Fusion: Present and Future

ABSTRACTDielectric insulator materials have played a critical role in the development of high peak power solid state lasers for use in inertial confinement fusion research: as laser gain media; as transparent substrates for lenses, mirrors, and polarizers; and as active optical materials in nonlinear harmonic generators and electro-optical devices. Materials have been developed which have exceptionally high resistance to damage in the presence of intense optical beams (> GW/cm2) and which possess other properties which optimize their functions in the laser systems. Fusion lasers built to date have been designed for “single shot” operation, and the dielectric insulator materials developed for use in them have had to function under only extremely low average power loading. As we look to the future, fusion laser systems will be required to operate repetitively (few Hz) and deliver high average power output (> MW) at an efficiency greater than 10 percent. Insulator materials for use in these systems must be selected and developed on the basis of their combined mechanical, thermal, and optical properties. In this presentation, I will summarize the important characteristics of currently used insulator materials, identify figures of merit for materials needed in future systems, and outline a methodology for identifying and evaluating new materials meeting the stringent performance requirements of future fusion laser systems.

A Method of Stabilizing the Output of a CO2 Laser for Use in Submillimeter-Wave Laser

A Method of Stabilizing the Output of a CO₂ Laser for Use in Submillimeter-Wave Laser

Compact, pulsed low-pressure far infrared laser for use in plasma diagnostics

The operation of a pulsed, watt-level, low-pressure far infrared (FIR) laser is described. Single mode output powers of 0.1-1 W are obtained from several molecular gases in the 300-1200 microm region. Plasma diagnostic applications are discussed.

Low-cost method for stabilization of a CO2 laser for use in far infrared laser pumping

A simple and inexpensive technique for stabilization of a CO2 laser used to optically pump a far infrared waveguide laser is discussed. The technique uses the fact that the output power of the CO2 laser varies as the output frequency is swept through the Doppler profile of the emission line. Stabilization is obtained by adjusting the mirror separation and forcing the output power to remain constant at the level corresponding to the desired pump frequency.

A simple first positive system nitrogen laser for use in optical fiber measurements

A near infrared laser operating on several transitions of the first positive system of N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> was developed for measurements associated with optical fibers. The laser features a simple, longitudinal, segmented design giving pulsewidths of 60 to 80 ns full width at half maximum (FWHM) and peak powers of over 600 W in the 0.86 to 0.89 μm region in addition to significant output near 1.04 and 1.23 μm. Backscatter-reflection returns from optical fibers have been obtained using the laser.

Progress at the Central Laser Facility

The decision of the Science Research Council to set up a central laser facility at the Rutherford Laboratory was announced in the December 1975 issue of the Physics Bulletin. It was then noted that the initial installation would be a large neodymium–glass laser for use in the study of laser–matter interactions but that the programme could include developmental work on other high power laser systems.

Optically pumped FIR lasers: Frequency and power measurements and laser magnetic resonance spectroscopy

Optically pumped FIR lasers are currently in use in both frequency metrology and laser magnetic resonance spectroscopy programs in the NBS Boulder labs. The laser for use in frequency metrology is a CW 71 μm methyl alcohol waveguide laser with over 100 mW output for frequency synthesis. Another laser with an intracavity absorption cell for laser spectroscopy has been constructed and is nearly transversely pumped. The metrology technique used to measure the frequency of these lasers is briefly reviewed and a unique power meter is described.

Recent advances in tunable lasers

This review of recent progress in understanding and developing tunable infrared lasers for use in highresolution spectroscopy and photochemistry covers work done at MIT Lincoln Laboratory on spin-flip Raman lasers, optically pumped semiconductor lasers, nonlinear frequency mixing in crystals, and optically pumped gas lasers.