Diffraction characteristics of general dielectric planar (slab) gratings and surface-relief (corrugated) gratings are reviewed. Applications to laser-beam deflection, guidance, modulation, coupling, filtering, wavefront reconstruction, and distributed feedback in the fields of acoustooptics, integrated optics, holography, and spectral analysis are discussed. An exact formulation of the grating diffraction problem without approximations (rigorous coupled-wave theory developed by the authors) is presented. The method of solution is in terms of state variables and this is presented in detail. Then, using a series of fundamental assumptions, this rigorous theory is shown to reduce to the various existing approximate theories in the appropriate limits. The effects of these fundamental assumptions in the approximate theories are quantified and discussed.

Analysis and applications of optical diffraction by gratings

A general formula is given that expresses frequency chirping in some types of external intensity modulators, such as the loss modulator, directional-coupler-type modulator, Mach-Zehnder interferometry-type modulator, and total-internal-reflection-type modulator. The chirping phenomenon treated is caused by the phase modulation due to an accompanied refractive index change. It is uniquely expressed in terms of an alpha -parameter that contributes to frequency chirping in the same manner as in the direct modulation of a semiconductor laser. In addition, the transmission bandwidth of a single-mode fiber system using an external modulator is discussed and compared with the results obtained utilizing direct laser modulation. >

Frequency chirping in external modulators

A theoretical analysis of the metal‐oxide‐metal (MOM) antenna/diode as a detector of microwave and infrared radiation is presented with the experimental verification conducted in the far infrared. It is shown that the detectivity at room temperature can be as high as 1010 W−1 Hz1/2 at frequencies of 1014 Hz in the infrared. As a result, design guidelines are obtained for the lithographic fabrication of thin‐film MOM structures that are to operate in the 10‐μ region of the infrared spectrum.

The MOM tunneling diode - Theoretical estimate of its performance at microwave and infrared frequencies

Nanometer thin-film Ni-NiO-Ni diodes for detection and mixing of 30 THz radiation

Recent progress in the dynamic single-mode (DSM) semiconductor lasers in the wavelength of 1.5-1.6\mu m are reviewed and the basic principle of DSM operation is given. Study of the DSM laser is originated for application to the wide-band optical-fiber communication in the lowest loss wavelength region of 1.5 to 1.65 μm. A DSM laser consists of a mode-selective resonator and a transverse-mode-controlled waveguide, such as the narrow-striped distributed-Bragg-reflector (DBR) laser, so as to maintain a fixed axial mode under the rapid direct modulation. The technology of monolithic integration for optical circuits is applied to realize some of DSM lasers. Structures, static and dynamic characteristics of lasing wavelength, output power, and reliability of the art DSM lasers are reviewed. The dynamic Spectral width of 0.3 nm, the output power of a few milliwatts, and the reliability over a few thousand hours are reported for experimental DSM lasers.

Dynamic single-mode semiconductor lasers with a distributed reflector

Coherent coupling of 10.6‐μm radiation into high‐resistance photolithographically fabricated metal‐oxide‐metal tunnel junctions has been demonstrated in direct detection experiments.

Coupling characteristics of thin‐film metal‐oxide‐metal diodes at 10.6 μ

A large‐optical‐cavity injection laser with low‐loss distributed Bragg reflectors has been realized. The temperature dependence of threshold current and of lasing wavelength clearly showed the DBR mode of operation. At room temperature, the lowest threshold current density thus far achieved was 7 kA/cm2. A coupling coefficient of around 50 cm−1 was estimated from the spectral bandwidth and from the intensity distribution of light scattered from the DBR region.

Large‐optical‐cavity GaAs‐ (GaAl)As injection laser with low‐loss distributed Bragg reflectors

Integration of an intensity light modulator and a LOC‐DBR laser on a single chip has been demonstrated. The injection‐type modulator gives a variable loss (or gain) to the laser light, coupled to it via an interconnecting waveguide, and thus modulates its intensity in accordance with the injected current of the modulator. An extinction ratio of more than 10 was obtained.

Monolithic integration of GaAs-(GaAl)As light modulators and distributed-Bragg-reflector lasers

Blazed gratings with a theoretical blaze angle of 35 degrees 16' are etched into (110) GaAs surfaces by preferential chemical etching, using a photoresist mask. A maximum total diffraction efficiency of 15% was measured at 6328 A from a blazed grating with a 2.23-microm period, and the diffracted light was concentrated in a single order. To demonstrate the applicability of such gratings in integrated optics, gratings with periods in a 3000- to 5000-A range were made, and epitaxial growth on (110) GaAs substrates was carried out using a method of growth that deposits high-quality, nearly defect-free layers on such substrates.

Preferential chemical etching of blazed gratings in (110)-oriented GaAs

Integration of a GaAs‐ (Ga1−xAlx)As LOC‐DBR laser with a detector is demonstrated. For integrated laser‐detector pairs in which the laser output is coupled to the detector via a 460‐μm‐long interconnecting waveguide, differential transfer efficiencies around 1% are measured. Threshold current densities as low as 6.4 kA/cm2 around room temperature are obtained.

Shyh Wang

Papers

Coupling characteristics of thin‐film metal‐oxide‐metal diodes at 10.6 μ

Large‐optical‐cavity GaAs‐ (GaAl)As injection laser with low‐loss distributed Bragg reflectors

Monolithic integration of GaAs-(GaAl)As light modulators and distributed-Bragg-reflector lasers

Preferential chemical etching of blazed gratings in (110)-oriented GaAs

p‐n junction detector directly integrated with (Ga1−xAlx)As LOC‐DBR laser