WAVELENGTH TUNABLE LASER, WAVELENGTH TUNABLE LASER MODULE, AND METHOD OF MANUFACTURING LAYER STRUCTURE OF WAVELENGTH TUNABLE LASER
A wavelength-tunable laser includes a substrate, a waveguide layer over the substrate, and a cladding over the waveguide layer. The wavelength-tunable laser further includes an active layer in a part of the waveguide layer, and a tunable wavelength filter in at least one end region of the waveguide layer in a direction along which light is to be guided.
1 - 7 . (canceled)
8 . A method of manufacturing a layer structure of a wavelength-tunable laser including, in order, an n-type substrate, a waveguide layer including an active layer and a bulk core layer, and a p-type cladding layer, the method comprising:
growing a semiconductor crystal for the active layer on the n-type substrate;
processing the grown semiconductor crystal for the active layer into the active layer;
butt-joint growing a semiconductor crystal for the bulk core layer around the active layer;
growing an undoped semiconductor crystal on the semiconductor crystal for the bulk core layer;
removing at least the undoped semiconductor crystal on the active layer;
forming a tunable wavelength filter in at least one end region of the semiconductor crystal for the bulk core layer; and
growing a semiconductor crystal for the p-type cladding layer.
9 . The method according to claim 8 , wherein the undoped semiconductor crystal comprises intrinsic InP.
10 . The method according to claim 8 , wherein the tunable wavelength filter comprises a distributed Bragg reflector (DBR).
11 . The method according to claim 8 , wherein the active layer comprises a strain InGaAs/InGaAs multiple quantum well (MQW).
12 . The method according to claim 8 , further comprising:
forming a diffraction grating between the bulk core layer and the p-type cladding layer in the at least one end region where the tunable wavelength filter is formed.
13 . The method according to claim 8 , wherein the n-type substrate comprises InP, and wherein the bulk core layer comprises InGaAs having a composition that lattice-matches InP.
14 . The method according to claim 8 , wherein growing the undoped semiconductor crystal comprises growing the undoped semiconductor crystal to a thickness of about 20 nm to about 500 nm.
15 . A wavelength-tunable laser comprising:
a substrate;
a waveguide layer over the substrate;
a cladding over the waveguide layer;
an active layer in a part of the waveguide layer; and
a tunable wavelength filter in at least one end region of the waveguide layer in a direction along which light is to be guided.
16 . The wavelength-tunable laser according to claim 15 , further comprising a barrier region between the waveguide layer and the cladding, the barrier region disposed on at least a part of the waveguide excluding the active layer.
17 . The wavelength-tunable laser according to claim 16 , wherein
the barrier region is configured to supply a current which bypasses the barrier region to the active layer.
18 . The wavelength-tunable laser according to claim 16 , wherein
the barrier region is made of a first semiconductor material,
the cladding is made of a second semiconductor material, and
a doping concentration of the barrier region is lower than a doping concentration of the cladding.
19 . The wavelength-tunable laser according to claim 17 , wherein
the barrier region is made of a first semiconductor material,
the cladding is made of a second semiconductor material, and
a doping concentration of the barrier region is lower than a doping concentration of the cladding.
20 . The wavelength-tunable laser according to claim 15 , further comprising
a first electrode pad for injecting a current into the active layer;
a second electrode pad for injecting a current into the tunable wavelength filter;
a third electrode pad for injecting a current into at least a part of the waveguide layer not including the active layer or the tunable wavelength filter; and
a resistance portion that connects at least one of the second electrode pad and the third electrode pad to the first electrode pad.
21 . A wavelength-tunable laser module comprising:
a wiring substrate, and
a wavelength-tunable laser according to claim 15 , the wavelength-tunable laser mounted on the wiring substrate,
wherein the wiring substrate includes:
a first substrate electrode pad for injecting a current into the active layer of the wavelength-tunable laser,
a second substrate electrode pad for injecting a current into the tunable wavelength filter of the wavelength-tunable laser,
a third substrate electrode pad for injecting a current into at least a part of the waveguide layer not including the active layer or the tunable wavelength filter, and
a resistor that connects at least one of the second substrate electrode pad and the third substrate electrode pad to the first substrate electrode pad.
22 . The wavelength-tunable laser module according to claim 21 , wherein the resistor is a variable resistor.