Hans W. Mocker

Coherent CO 2 laser communication system with modulable retroreflectors

A coherent CO(2) laser communication system that yields high-quality voice communications between a transmit-receive station and a remote site (24 km) where modulable retroreflectors are located was developed. The potential range capability of this system was 80 km, and the system was improved by 20 dB in the signal-to-noise ratio over a direct-detection system.

Airborne laser Doppler velocimeter

A CO(2) laser Doppler detection system has been developed to measure remotely the true airspeed of an aircraft. The system uses a 50-W sealed-off CO(2) laser in a homodyne detection system employing a collinear optical telescope, a HgCdTe detector, and a frequency tracking loop. The system was successfully flight tested on a NASA Convair 990 research aircraft during December 1971 and June 1972. The results indicate that an airspeed measurement under clear weather conditions is feasible up to an altitude of 3000 m with an error of less than 0.5%.

A 10.6-μ Optical Heterodyne Communication System

A 10.6-micro optical heterodyne communication system is described that uses two stable single mode and single frequency CO(2) lasers of high frequency stability. Wavelength control on both lasers allows the use of one and the same transition of the rotation-vibration band of CO(2) around 10.6 micro. The system has a bandwidth of 1 MHz, and simultaneous operation in baseband and on a 50-kHz carrier has been achieved. Heterodyne detection with mercury cadmium telluride detectors yielded signal-to-noise ratios within 3 dB of the coherent photon noise limit.

High accuracy laser Doppler velocimeter using stable long-wavelength semiconductor lasers.

Doppler velocimeters for remote velocity sensing require a compact and miniaturized system. We report the achievement of an eye-safe Doppler velocimeter at 1.54microm using InGaAsP diodes reduced in linewidth by external cavity stabilization techniques. Linewidth of the diodes was of the order of 40 kHz allowing for a sub-cm/s velocity resolution over long distances (i.e., 100 m).

PRESSURE AND CURRENT DEPENDENT SHIFTS IN THE FREQUENCY OF OSCILLATION OF THE CO2 LASER

The shift of the frequency of oscillation of the 00°1–10°0 rotation‐vibration band at 10.6 μ of a CO2 laser has been investigated as a function of total pressure, CO2 partial pressure, discharge current, and cavity mode position. The measurements were made by heterodyning two passively stabilized CO2 lasers, both oscillating in a single transverse mode and single frequency at the P branch of the 00°1–10°0 rotation‐vibration band of CO2. The result yielded a 5–8 MHz/torr frequency shift toward red due to an increase in total pressure and a 500–900 kHz/mA shift toward blue due to an increase in excitation. The amount of frequency shift due to excitation was found to be independent of the location of the cavity resonance with respect to the Doppler center. The dependence on CO2 partial pressure was also determined.

Laser Doppler optical air-data system: feasibility demonstration and systems specifications

A compact laser Doppler velocimeter with diode-pumped solid-state laser technology at 1.06 µm and a novel solid-block beam-splitting interferometer was demonstrated. This system allows for accurate Doppler velocity measurements even in a vibration environment. A comparison of the backscatter measurements with a backscatter sonde from the University of Wyoming showed excellent agreement. Based on demonstrated performance and technology projection, the system specifications of an optical air-data system at 2.015 µm are determined, and a detailed design concept is presented. In addition, the potential for a multifunctional sensor that can determine air data and detect wind shear and wake vortices is addressed.

Rapidly tunable CO 2 TEA laser

The new method described in this publication has demonstrated rapid and accurate random access tuning over seventy CO/sub 2/ TEA laser lines. The technique described here uses a continuously rotating grating and a wavelength selection based on the exact firing time of the TEA laser with respect to the angular position of the grating. The angular position of the grating determined by an angular encoder. The faceted grating structure is driven by a synchronous motor at a speed of 1000 rpm. The TEA laser is accurately triggered once for each facet of the grating structure.

Laser helmet-mounted sight

A laser diode measurement concept is described that can be effectively used in a helmet mounted sight system; it offers a factor of 5 resolution improvement over conventional optical sensing techniques. It also has no moving parts and eliminates the compensation problems associated with helmet mounted metal in magnetic approaches. In the laser helmet mounted sight approach, the feedback from a helmet mounted reflector interacts with an airframe mounted diode to form a 3 mirror laser cavity; this semi-conductor laser cavity technique is used to provide 20 micrometers range resolution for the triangulation of fixed reflection points on the helmet. Geometric and radiometric models have been developed that show the feasibility of this approach. Geometric models include a discussion of resolution requirements. Radiometric models include a discussion of the laser cavity conceptual approach and a performance analysis of resolution and detectability.

The CO[sub]2[/sub] Waveguide Laser And Its Applications

This paper discusses the advances in CO2 waveguide laser technology and compares the output characteristics of the waveguide laser with those of the conventional CO2 laser both operating at 10.6 micron. Since the first demonstration of the waveguide laser in 1972 significant strides have been made towards the achievement of an operational unit that can be used for many electro-optical systems application. Especially due to operation at high pressures a large tunability (>1 GHz) can be obtained and applications such as tunable sources for satellite communication and doppler tracking radar appear now feasible. Beam confinement of the mode to narrow capillaries made of high strength dielectric materials gives the laser a new dimension in terms of rigidity and miniaturization. Applications appear now feasible that have thus far been a domain of conventional light sources. Sealed-off lasers are now available that do not require a gas supply and a vacuum pump. High stability waveguide lasers have been built with both excellent short-term and long-term stabilities comparable to the best conventional lasers. Thus, compact coherent receivers can be built which are superior to straight detection receivers. With this potential it is no surprise that the waveguide laser is finding every day many new applications for which lasers have not been considered.

Characteristics of a λ/2 Kerr Cell Ruby Oscillator for Use as an Optical Radar (Lidar)

A Q-switched ruby laser has been developed that is useful as an optical radar for clear air turbulence detection. The output is a single clean pulse of 35 MW, free of noise sources such as spontaneous emission, superradiance, and after-pulsing. A comparison is made with the standard quarter-wave mode of operation.