1. A semiconductor laser diode, comprising:
an active layer;
an n-type cladding layer made of a first group III-V compound semiconductor material;
a first guiding layer provided between the active layer and the n-type cladding layer, the first guiding layer being made of AlGaInAs with a first band gap wavelength and a first conduction band level; and
a second guiding layer provided between the first guiding layer and the active layer, the second guiding layer being made of a second group III-V compound semiconductor material with a second band gap wavelength and a second conduction band level lower than the first conduction band level in the first guiding layer, the first band gap wavelength of the first guiding layer being shorter than the second band gap wavelength,
wherein the first guiding layer is a p-type layer.
2. The semiconductor laser diode according to claim 1,
wherein the first guiding layer has a hole concentration greater than 1\xd71016 cm\u22123.
3. The semiconductor laser diode according to claim 1,
wherein the first guiding layer has a hole concentration smaller than 1\xd71018 cm\u22123.
4. The semiconductor laser diode according to claim 1,
wherein the second guiding layer is a p-type layer.
5. The semiconductor laser diode according to claim 4,
wherein the second group III-V compound semiconductor material has a hole concentration greater than 1\xd71016 cm\u22123.
6. The semiconductor laser diode according to claim 4,
wherein the second group III-V compound semiconductor material has a hole concentration smaller than 1\xd71018 cm\u22123.
7. The semiconductor laser diode according to claim 1 ,
wherein the second III-V compound semiconductor material is selected from a group of AlGaInAs and GaInAsP, and
wherein the first group III-V compound semiconductor material is n-type InP.
8. The semiconductor laser diode according to claim 1,
wherein the first guiding layer has a thickness greater than 30 nm.
9. The semiconductor laser diode according to claim 1,
wherein the active layer has a multiple quantum well structure with a plurality of barrier layers and a plurality of well layers, and
wherein the second guiding layer has a thickness greater than a thickness of the barrier layer.
10. The semiconductor laser diode according to claim 9,
wherein the second guiding layer has a thickness greater than 20 nm.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An acoustic transducer that converts a mechanical motion into acoustical energy comprising:
a thin sheet diaphragm that is curved in a plane transverse to a first direction,
a support that fixes one generally linear portion of said diaphragm along said first direction, and
at least one actuator operatively coupled to said diaphragm and generally aligned with, but mutually spaced from said fixed generally linear portion in a second direction transverse to said first direction by a distance that produces a curvature of said diaphragm and that accommodates a movement of said diaphragm that corresponds to the travel of said actuator, said diaphragm movement being amplified with respect to said actuator travel and generally transverse to the direction of said actuator travel.
2. The acoustic transducer of claim 1 wherein said at least one actuator is characterized by a high force and short linear travel.
3. The acoustic transducer of claim 1 wherein said at least one actuator is a piezo actuator.
4. The acoustic transducer of claim 1 wherein said curvature is generally parabolic.
5. The acoustic transducer of claim 2 further comprising a seal at at least a portion of the periphery of said diaphragm to assist in maintaining the acoustic pressure gradient across said transducer.
6. The acoustic transducer of claim 5 wherein said actuator is a piezo bimorph drive, and said operative coupling is generally at the center of said diaphragm to divide said diaphragm into two sections, and where said diaphragm curvature in one section is convex, and in the other section is concave.
7. An acoustic transducer according to any of claims 4 or 5 for use in combination with a video screen display wherein said support overlies the screen display and said diaphragm is generally coextensive with, and closely spaced from, said screen display.
8. The acoustic transducer of claim 7 wherein said actuator is a piezoelectric drive and said diaphragm is formed of aan optically clearfilm.
9. The acoustic transducer of claim 7 wherein said diaphragm is fixed along its vertical centerline, and said actuator is a pair of actuators that are each operatively coupled to one lateral edge of said diaphragm to form two diaphragm sections each generally coincident with about half of the screen display.
10. The acoustic transducer of claim 8 wherein said piezoelectric drive is a single layer piezo actuator.
11. The acoustic transducer of any of the preceding claims further comprising an electronic drive circuit operatively connected to said power actuators.
12. The acoustic transducer of claim 11 wherein said drive circuit comprises an active filter and an amplifier.
13. The acoustic transducer of claim 12 wherein said drive circuit further comprises a step-up transformer and a resistor connected in series with said transformer to control high frequency response.
14. The acoustic transducer of claim 12 wherein said drive circuit drives said actuator to control operation at a main resonance in the transducer output.