Accession Number : AD0917035

Title :   Long Wavelength Modulation Techniques (10.6 Micrometers).

Descriptive Note : Final technical rept. 1 Oct 72-15 Nov 73,

Corporate Author : HUGHES RESEARCH LABS MALIBU CA

Personal Author(s) : Lotspeich, James F.

Report Date : JAN 1974

Pagination or Media Count : 110

Abstract : Wideband, low power electro-optic modulators of optical waveguide structure have been developed for CO2 laser applications, in response to a need for relieving an excessive power burden exhibited by bulk, diffraction-limited devices at long wavelengths. The waveguide modulators are composed of very thin layers of single crystal GaAs, approximately 0.001 in. thick, bounded on both sides by evaporated films of lower refractive index material: CdTe or As2S3. External metal films are provided for application of signal voltages. Coupling to the modulators was achieved with both prisms and ionmachined gratings, yielding maximum efficiencies of 68 and 10%, respectively. Output beam profile and divergence measurements showed well collimated beams with little or no sidelobe structure. Minimum propagation loss of the experimental waveguide samples studied was 0.69 dB/cm for TE modes. Both intensity modulation and beam deflection were observed in several prototype devices, and one 50-pF modulator having a 3-dB rolloff around 60 MHz showed useful modulation out to 200 MHz. The basic capability for advanced design modulators of this type to exhibit 200 MHz bandwidth with a driver power of 20 W for 100% modulation depth was shown analytically. The 10.6 micrometers power handling capability was demonstrated experimentally to be in excess of 200 mW; and a thermal analysis indicated temperature rises of less than 0.5 C for a modulator of the smallest practicable size. (Author)

Descriptors :   *MODULATION), *MODULATORS), (*CARBON DIOXIDE LASERS, (*INFORMATION PROCESSING, LASER COMMUNICATIONS), (*ELECTROOPTICS, LONG WAVELENGTHS, WAVEGUIDES, OPTICS, DIFFRACTION, SINGLE CRYSTALS, GALLIUM ARSENIDES, REFRACTIVE INDEX, CADMIUM ALLOYS, TELLURIDES, ARSENIC COMPOUNDS, SULFIDES, EFFICIENCY, METAL FILMS, LASER BEAMS, SIDELOBES, PROPAGATION, INTENSITY, THERMAL PROPERTIES, BANDWIDTH, BROADBAND, COUPLING(INTERACTION), POLISHES, BONDING.

Subject Categories : Lasers and Masers
      Non-radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE