Distributed feedback laser diode

Claim 2

A distributed feedback laser diode comprising: a substrate; a planar waveguide structure including a first light confining layer, a second light confining layer and an active layer therebetween; a diffraction grating formed between said waveguide structure and said substrate; partially reflecting films formed on opposing ends of said waveguide structure; electrodes formed respectively below said substrate and above said waveguide structure; said diffraction grating having a phase shift at a portion thereof away from ends thereof producing thereby a phase shift amount of λ/8 to 3λ/16 between pitches of said diffraction grating on either side of said phase shift.

Claim 3

A distributed feedback laser diode comprising: a diffraction grating formed on a substrate, said diffraction grating having a phase shift at a portion thereof away from ends thereof producing thereby a phase shift amount of λ/8 to 3λ/16 between pitches of said diffraction grating on either side of said phase shift; a guided layer formed through said diffraction grating on said substrate; an active layer formed through said diffraction grating on said substrate; a cladding layer formed on said active layer; a current blocking layer formed on said cladding layer; a buried layer formed on said current confining layer; a cap layer formed on said buried layer; a pair of electrodes respectively provided on outer surfaces of said substrate and cap layer; and a pair of partially reflecting films respectively provided on both end planes of a layered structure thus fabricated on said substrate.

Claim 4

A distributed feedback laser diode comprising: a diffraction grating formed on a substrate, said diffraction grating having a phase shift at a portion thereof away from ends thereof producing thereby a phase shift amount of λ/8 to 3λ/16 between pitches of said diffraction grating on either side of said phase shift; a guided layer formed through said diffraction grating on said substrate; an active layer formed through said diffraction grating on said substrate; a cladding layer formed on said active layer; a current blocking layer formed on said cladding layer; a buried layer formed on said current confining layer; a cap layer formed on said buried layer; a pair of electrodes respectively provided on outer surfaces of said substrate and cap layer; and a pair of partially reflecting films respectively provided on both end planes of a layered structure thus fabricated on said substrate.

Claim 5

A distributed feedback laser diode according to claim 2; wherein a pair of grooved are formed in parallel from said cladding layer to said substrate to provide a mesa stripe therebetween, said grooves being perpendicular to repeating lines of said diffraction grating.

Claim 6

A distributed feedback laser diode according to either of claims 1 and 2; wherein an effective value of said phase shift amount of λ/8 to 3λ/16 is increased to approximately λ/4 in a case where a maximum rate of light output is produced.

Claim 7

A distributed feedback laser diode according to claims 1 and 2, wherein said phase shift is provided in the center position of said diffraction grating.

Claim 8

A distributed feedback laser diode as recited in claim 1, wherein said first light confining layer is a guide layer and said second light confining layer is a cladding layer.

Claim 9

A distributed feedback laser diode as recited in claim 6, wherein said diffraction grating is formed by an undulating surface between said guide layer and said substrate.

Claim 10

A distributed feedback laser diode as recited in claim 2, wherein said partially reflecting films has a reflection coefficient between 0.5% and 1%.