Vertical cavity surface emitting laser
A vertical cavity surface emitting laser is provided which controls the reflectivity at the middle portion and the peripheral portion of the mirror with a simple structure to cause oscillation of a single lateral mode by use of a mirror having the refractive index changing periodically in the mirror plane direction. The vertical cavity surface emitting laser.
1. A vertical cavity surface emitting laser comprising:
first and second mirrors as reflecting mirrors included in a resonator;
an active layer positioned between the first mirror and the second mirror; and
a current-confining layer for confining an electric current injected into the active layer, wherein
the first mirror includes a periodic refractive index structure in a plane direction of the mirror, and a phase-shift part, whereby a light beam introduced perpendicularly to a mirror plane resonating in the plane direction of the mirror and is reflected in a direction perpendicular to the plane direction of the mirror,
a reflectivity of a specific resonant mode in a neighboring region to the phase-shift part is lower than a reflectivity in regions other than the neighboring region,
the periodic refractive index structure has a one-dimensional periodic structure in which a refractive index changes periodically in one direction in the mirror plane,
the one-dimensional periodic structure is a one-dimensional photonic crystal, and therein two or more phase-shift portions are provided at positions where light in the plane direction of the mirror that passes through each phase-shift portion does not interfere,
the current-confining layer is an oxidation aperture with a diameter in a range of from 5 to 8 μm, and
the phase-shift part is positioned outside the oxidation aperture.
2. The vertical cavity surface light emitting laser according to claim 1 , wherein the specific resonant mode is formed by the current-confining layer.
3. The vertical cavity surface light emitting laser according to claim 1 , wherein the neighboring region covers 4 to 10 periods of the periodic refractive index structure from the phase shift part.
4. The vertical cavity surface emitting laser according to claim 1 , wherein the neighboring region covers 4 to 5 periods of the photonic crystal from the phase-shift part.
5. A vertical cavity surface emitting laser comprising:
first and second mirrors as reflecting mirrors included in a resonator;
an active layer positioned between the first mirror and the second mirror; and
a current-confining layer for confining an electric current injected into the active layer, wherein
the first mirror includes a periodic refractive index structure in a plane direction of the mirror, and a phase-shift part, whereby a light beam introduced perpendicularly to a mirror plane resonating in the plane direction of the mirror and is reflected in a direction perpendicular to the plane direction of the mirror,
a reflectivity of a specific resonant mode in a neighboring region to the phase-shift part is lower than a reflectivity in regions other than the neighboring region,
the periodic refractive index structure has a one-dimensional periodic structure in which a refractive index changes periodically in one direction in the mirror plane,
the one-dimensional periodic structure is a one-dimensional photonic crystal, and therein two or more phase-shift portions are provided at positions where light in the plane direction of the mirror passes through each phase-shift portion does not interfere, and
a gap is provided between the first mirror and the second mirror, the gap being adjacent to an upper one of the first and second mirror.
6. The vertical cavity surface light emitting laser according to claim 5 , wherein the specific resonant mode is formed by the current-confining layer.
7. The vertical cavity surface light emitting laser according to claim 5 , wherein the neighboring region covers 4 to 10 periods of the periodic refractive index structure from the phase shift part.
8. The vertical cavity surface emitting laser according to claim 5 , wherein the neighboring region covers 4 to 5 periods of the photonic crystal from the phase-shift part.