Tunable laser diode
An oscillation wavelength adjustment type TLD for adjusting a control amount of a resonator length L, independently from physical property values of a waveguide material when a waveguide is used in the phase adjustment, without an external resonator structure in accordance with a MEMS technology employs a reflective phase adjuster including a multi-mode interference waveguide, which is optically coupled to an optical gain waveguide and has a configuration including one input port and five output ports, and a reflective delay line array connected to an output waveguide on a side of the five output ports of the multi-mode interference waveguide. Five reflective delay lines provided in the reflective delay line array are capable of adjusting the intensity of reciprocating light in accordance with a wavelength change of transmitted light.
1 . An oscillation wavelength adjustment type tunable laser diode comprising:
an optical gain waveguide configured to generate and amplify light;
a multi-mode interference waveguide configured to include M input ports and N output ports (where M is a natural integer and N is a positive integer equal to or greater than 2); and
a reflective delay line array including N reflective delay lines connected to a side of the N output ports of the multi-mode interference waveguide, each of N reflective delay lines being terminated by a reflector configured to reflect the light,
the optical gain waveguide, the multi-mode interference waveguide, and the reflective delay line array being integrated on a top surface of an identical substrate,
wherein each of the N reflective delay lines is provided with an electro-absorption modulator, and when t i (i=0, 1, 2, . . . , N−1) denotes an electric field transmittance of reciprocating light in each of the N reflective delay lines, each of the electro-absorption modulator is configured to control an intensity of the reciprocating light so that a total value of the electric field transmittance
(
∑
i
=
0
N
-
1
t
i
)
is constant, and
wherein the N reflective delay lines are configured to adjust the intensity of the reciprocating light in accordance with a wavelength of the light transmitted through the N reflective delay lines.
2 . The tunable laser diode according to claim 1 , wherein the N reflective delay lines are configured to adjust the intensity of the reciprocating light by an electric signal applied from outside.
3 . An oscillation wavelength adjustment type tunable laser diode comprising:
an optical gain waveguide configured to generate and amplify light;
a multi-mode interference waveguide configured to include M input ports and N output ports, where M is a natural integer and N is a positive integer equal to or greater than 2; and
a reflective delay line array including N reflective delay lines connected to a side of the N output ports of the multi-mode interference waveguide, each of N reflective delay lines being terminated by a reflector configured to reflect the light,
wherein the optical gain waveguide, the multi-mode interference waveguide, and the reflective delay line array being integrated on a top surface of an identical substrate,
each reflector of the N reflective delay lines having a wavelength dependent electric field reflectance r i (i=0, 1, 2, . . . , N−1) of reciprocating light in each of the N reflective delay lines, and
a peak wavelength and a shape of a reflection spectrum of the each reflector are adjusted so that a total value of the electric field reflectance
(
∑
i
=
0
N
-
1
r
i
)
is constant in a certain wavelength section.