E. H. Turner

Electrooptic light modulators

The field of electrooptic light modulation by means of the Pockels and Kerr effects in crystals is summarized with particular attention to communications applications using the optical maser. AH available data on electrooptic materials are tabulated, and design considerations and operating principles for various modulator configurations are outlined.

Electrooptic Light Modulators

The field of electrooptic light modulation by means of the Pockels and Kerr effects in crystals is summarized with particular attention to communications applications using the optical maser. All available data on electrooptic materials are tabulated, and design considerations and operating principles for various modulator configurations are outlined.

Characteristics of Ti-diffused lithium niobate optical directional couplers

The dependence of the coupling strength of titanium-diffused lithium niobate directional couplers upon fabrication parameters and guided wavelength has been investigated. Measurements of the coupling strength as a function of interguide separation have been made at He-Ne, GaAs, and Nd:YAG wavelengths. To good approximation, the coupling strength depends exponentially upon guide separation. Rather strong dependence upon the metal thickness diffused and the guided wavelength were observed. Good comparison was obtained with theoretical results calculated using an effective index method. Transfer lengths as short as 200 microm have been obtained. Fabrication parameters for which the coupling strength for the TE and TM modes are equal were determined.

A bistable Fabry‐Perot resonator

We propose and demonstrate the operation of a novel bistable optical device that exhibits differential gain and can function as an optical switch, limiter, or optical memory element.

Efficient strip‐waveguide modulator

A strip‐waveguide electro‐optic phase modulator has been fabricated in Ti‐diffused LiNbO3. For a modulation index of 1 rad at 0.63 μm, the modulating voltage is 0.3 V and the power is 1.7 μW/MHz of bandwidth.

Lithium niobate ridge waveguide modulator

A narrow ridge was ion‐beam etched on an outdiffused LiNbO3 crystal to form a single‐mode waveguide confining the beam in both transverse dimensions. Electrodes were evaporated along the ridge to produce a very efficient electro‐optic phase modulator requiring a power of 20 μ W/MHz of bandwidth and a voltage of 1.2 V to produce a modulation index of 1 rad.

Thin‐film LiNbO3 electro‐optic light modulator

An out‐diffused planar optical waveguide in LiNbO3 has been used to produce an efficient broad‐band electro‐optic phase modulator. The ratio of modulation index η and voltage is 0.13 V−1, the maximum base bandwidth with 50‐Ω load is 3.2 GHz, and the modulating power per unit bandwidth for η=1 rad is 0.2 mW/MHz.

Faraday rotation in highly birefringent optical fibers

Faraday rotation is obtained in highly birefringent single-mode fibers by using alternating or periodically spaced regions of magnetic field. This approach has potential applications in isolators, circulators, combination tuning and unidirectional elements, and for studying fiber birefringence.

Conversion of cw light into a train of subnanosecond pulses using frequency modulation and the dispersion of a near‐resonant atomic vapor

Sinusoidally frequency‐modulated cw laser light is converted into a train of repetitive short pulses by passing it through a nearly resonant atomic vapor. Using a 200‐MHz modulation frequency and sodium vapor, pulses as short as 240 psec, having peak powers of 6.3 times the input power, have been obtained at 5890 A. Calculation and experiment are in good agreement.

ELECTRO‐OPTIC ELIMINATION OF SPATIAL HOLE BURNING IN LASERS

By modulating the position of the standing‐wave field inside the laser cavity electro‐optically with certain discrete amplitudes, the population inversion can be made uniform for all positions along the axis. This produces spontaneous single‐frequency output for homogeneously broadened lasers. It is shown experimentally that maximum stable single‐frequency operation of a Nd : YAG laser can be obtained with this technique. Simultaneous doubling of the single frequency is also observed.