Abstract: The invention provides an optical waveguide for enabling the reduction of a coupling loss caused by difference in the size of a mode field diameter between optical waveguide modes different in the mode field diameter and a coupling loss caused by reflection on a boundary caused by the difference of media and an optical device using it. Structure provided with a mode field diameter converter provided with an antireflection part required to reduce a coupling loss between a microoptical circuit and a single mode optical fiber is integrally produced using effective refractive index control based upon photonic crystal structure.

Abstract: The present invention provides a technique of reducing an incident/outgoing loss of a photonic crystal. On each of incident/outgoing sides of a photonic crystal, an antireflection layer made of a photonic crystal is disposed. At the incident side of a photonic crystal 200 having an effective refractive index n2, a photonic crystal 100 having an effective refractive index n1 satisfying the relation of n1<n2 is disposed, and the thickness of the photonic crystal 100 is controlled so that reflection components from interfaces 210 and 110 cancel each other out by interference, thereby reducing a total reflection loss on the incident side. The outgoing side is similarly constructed.

Abstract: An optical signal synthesizer having an optical slab waveguide constructed from three layers in which optical pulses are introduced. A first cut-away portion of the optical slab waveguide has a plano-concave shape serving as a plano-convex lens which collimates the introduced optical pulses, a second cut-away portion of the optical slab waveguide serving as a diffraction grating for parallel light beams in which the optical pulses are separated into every frequency, and a third cut-away portion of the optical slab waveguide has a plano-concave shape serving as a plano-convex lens by which the separated optical pulses are focused on a different spatial position associated with each frequency. A spatial light modulator is fabricated at the focusing position in the optical slab waveguide which allows the optical pulses subjected to optical modulation every frequency to pass therethrough according to an applied electrical signal.

Abstract: In the wavelength-division-multiplexed optical transmission, laser diodes of the number of multiplicity are disposed as a light source to configure a transmitter. However, since this method requires a large number of light sources and highly precise wavelength control, a cost and an apparatus are increased. An ultrashort pulse solid-state laser is used as the light source of the transmitter and its wide spectrum is taken out by a splitter to be assigned to each channel, so that the number of light sources can be reduced greatly. The transmitter requires high repetition rate such as 2.4 GHz, 10 HGz and the like as the repetition rate of the ultrashort pulse solid-state laser, while by configuring the resonator only by two components as shown in FIG. 1, the high repetition rate can be attained. Since each channel is produced passively from the splitter, very precise wavelength management is not required. The light source is made small and the number thereof is reduced.

Abstract: In a solid-state laser in which a gain crystal is polished to have the Brewster angle or a solid-state laser comprising a dichroic concave mirror to which light enters at an incidence angle which is not zero, astigmatism generally occurs in pumping light. By tilting a focusing lens for pumping light with respect to the optical axis of the pumping light, the astigmatism is compensated. The tilting angle is determined in such a manner that synthetic focusing points in the sagittal and tangential planes, of a series optical system of a focusing lens, a dichroic concave lens, and a gain crystal are calculated and the focusing points almost coincide with focusing points in a cavity mode.

Abstract: In a solid-state laser in which a gain crystal is polished to have the Brewster angle or a solid-state laser comprising a dichroic concave mirror to which light enters at an incidence angle which is not zero, astigmatism generally occurs in pumping light. By tilting a focusing lens for pumping light with respect to the optical axis of the pumping light, the astigmatism is compensated. The tilting angle is determined in such a manner that synthetic focusing points in the sagittal and tangential planes, of a series optical system of a focusing lens, a dichroic concave lens, and a gain crystal are calculated and the focusing points almost coincide with focusing points in a cavity mode.

Abstract: A compact solid-state laser has its cavity formed by the reflection surface of a gain crystal and the reflection surface of a chirped mirror. The pumping light is incident to the cavity through the reflection surface of the gain crystal or the chirped mirror, from which the laser output is led out. Forming the cavity solely by the gain crystal and chirped mirror enables the elimination of additional component parts for the compensation of dispersion, so that the whole laser system can be made compact and, consequently, the repetition frequency can be made higher.

Abstract: A compact solid-state laser has its cavity formed by the reflection surface of a gain crystal and the reflection surface of a chirped mirror. Pumping light is incident to the cavity through the reflection surface of the gain crystal or the chirped mirror, from which the laser output is led out. Forming of the cavity solely by the gain crystal and chirped mirror enables the elimination of additional component parts for the compensation of dispersion, thereby making the entire laser system compact, and consequently permitting an increase in the repetition frequency.

Abstract: A femtosecond pulse incident on a Mach-Zehnder interferometer is divided into two optical paths and thereafter synthesized again. The synthesized optical pulse is outputted as complementary two output optical pulses corresponding to the difference between optical paths. An optical interferometer for monitoring fluctuations of the optical path difference from one of two output optical pulses produced from an interferometer, effecting feedback on the optical path difference and providing an operation stabilized in a relation of 1/20 or less the central wavelength, and an optical signal synthesizer using the interferometer are provided.