Abstract: The present invention provides an external resonator-type wavelength tunable laser device that can properly fulfill a wavelength tuning function even with the use of a planar wavelength tunable reflector involving a considerable level of residual reflection. The external resonator-type wavelength tunable laser device includes a planar reflection structure enabling a reflection spectral peak wavelength to be varied and a semiconductor element as a semiconductor gain medium. The semiconductor gain medium is composed of a multiple quantum well in which product ?·L of optical confinement constant ? and semiconductor gain medium length L (?m) of a gain layer is at least 25 ?m and at most 40 ?m and in which gain peak wavelength ?0 (nm) observed during carrier injected with a maximum modal gain equal to an internal loss of the semiconductor gain medium is larger than ?3·?R/2+(?c+35) and smaller than (?(?·L)/7+8)·?R+(?(?·L)+?c+45).

Abstract: The present invention provides an external resonator-type wavelength tunable laser device that can properly fulfill a wavelength tuning function even with the use of a planar wavelength tunable reflector involving a considerable level of residual reflection. The external resonator-type wavelength tunable laser device includes a planar reflection structure enabling a reflection spectral peak wavelength to be varied and a semiconductor element as a semiconductor gain medium. The semiconductor gain medium is composed of a multiple quantum well in which product ?·L of optical confinement constant ? and semiconductor gain medium length L (?m) of a gain layer is at least 25 ?m and at most 40 ?m and in which gain peak wavelength ?0 (nm) observed during carrier injected with a maximum modal gain equal to an internal loss of the semiconductor gain medium is larger than ?3·?R/2+(?c+35) and smaller than (?(?·L)/7+8)·?R+(?(?·L)+?c+45).

Abstract: To facilitate phase adjustment in an external resonator type wavelength-variable laser. An external resonator type wavelength-variable laser (50) includes a semiconductor light amplifier (1), a wavelength selection filter (3) having periodic frequency characteristics, an external resonator (6), and a wavelength-variable filter (4). ?f is divided into one or more regions. The following conditions are satisfied for one ?fi region: mj=(j×?ffs)/?fFP where ?ffs: a period of the wavelength selection filter, ?fFP: a Fabry-Perot mode interval dependent on a length of the external resonator, j: an integer not smaller than 1 and not larger than (?fi/?ffs). A coefficient Mj is an integer obtained by rounding off the first digit after decimal point of the coefficient mj. A coefficient Ni,j is an integer obtained by discarding the first digit after decimal point of ?fi/(j×?ffs). In this regard, a relation of (|Ni,j×2?(Mj?mj)|<?/2) is satisfied for one j.

Abstract: An object of the invention is to provide an optical integrated device which enables to supply a wide range of variable wavelength and to reduce the coupling loss. The optical integrated circuit chip (10) includes a semiconductor optical amplifier section (20), a phase control section (18), a partially reflecting mirror (16) having optical power splitter function and a Mach-Zehnder optical modulator (22), wherein all elements are formed on a same substrate monolithically. On each facet of the optical integrated circuit chip (10), an Anti-Reflection coating (12, 14) is formed respectively. A lens (30), an optical filter (32) and an external resonator mirror (28) are located outside of the optical integrated circuit chip (10), wherein an external cavity laser is formed with a semiconductor optical amplifier (SOA) section (20) operating as gain section, a partially reflecting mirror (16) operating as first reflecting mirror and an external resonator mirror (28) operating as a second mirror.

Abstract: To provide a semiconductor laser diode and a semiconductor optical amplifier and an optical communication device incorporating the semiconductor laser diode or the semiconductor optical amplifier which enable low power consumption and high optical output. A semiconductor laser diode according to an embodiment of the present invention is a semiconductor laser diode 100 comprised of an active waveguide, the active waveguide including a first waveguide 11a that supplies a plurality of modes including a fundamental mode; and a second waveguide 12a that is wider than the first waveguide 11a and supplies a multimode, wherein the fundamental mode is provided as an oscillation light oscillated from the active waveguide.

Abstract: To facilitate phase adjustment in an external resonator type wavelength-variable laser. An external resonator type wavelength-variable laser (50) includes a semiconductor light amplifier (1), a wavelength selection filter (3) having periodic frequency characteristics, an external resonator (6), and a wavelength-variable filter (4). ?f is divided into one or more regions. The following conditions are satisfied for one ?fi region: mj=(j×?ffs)/?FP where ?ffs: a period of the wavelength selection filter, ?fFP: a Fabry-Perot mode interval dependent on a length of the external resonator, j: an integer not smaller than 1 and not larger than (?fi/?ffs). A coefficient Mj is an integer obtained by rounding off the first digit after decimal point of the coefficient mj. A coefficient Ni,j is an integer obtained by discarding the first digit after decimal point of ?fi/(j?ffs). In this regard, a relation of (|Ni,j×2?(Mj?mj)|<?/2) is satisfied for one j.

Abstract: To provide a semiconductor laser diode and a semiconductor optical amplifier and an optical communication device incorporating the semiconductor laser diode or the semiconductor optical amplifier which enable low power consumption and high optical output. A semiconductor laser diode according to an embodiment of the present invention is a semiconductor laser diode 100 comprised of an active waveguide, the active waveguide including a first waveguide 11a that supplies a plurality of modes including a fundamental mode; and a second waveguide 12a that is wider than the first waveguide 11a and supplies a multimode, wherein the fundamental mode is provided as an oscillation light oscillated from the active waveguide.