Patent US3871017A successfully refreshed from Google Patents.
US3871017A
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High-frequency phonon generating apparatus and method
Assignee: Massachusetts Institute of Technology
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Filing: 1972-06-27
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Granted: 1975-03-11
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Expires: 1992-06-27
Abstract
Abstract Apparatus for generating high frequency phonons wherein a multivalley semiconductor device is pumped and a shear stress or uniaxial stress exerted upon the device to produce differentvalued energy gaps within the semiconductor material. Phonon generating apparatus of more general nature is disclosed as are, also, systems to use the phonons, thus generated. The invention herein described was made in the course of contracts with the Office of the Secretary of Defense, Advanced Research Projects Agency.
Inventors
- 👤 Jr George W Pratt
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 08:45
CPC Classifications
H; H01; H01S; H01S4/00; B; B06; B06B; B06B1/00; B06B1/02; B06B1/04; H01S5/00; H01S5/06; H01S5/0607
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
208 words
A method of generating phonons, that comprises, providing a body of semiconductor having a multi-valley energy level band structure, that is, a semiconductor whose electron energy level band extrema are not at k 0, where k is vector pseudomomentum, so that degenerate valleys result from symmetry, said semiconductor having a conduction band of electron energy levels and a valence band of electron energy levels, said conduction band including unfilled levels and said valence band including filled levels in a condition of thermal equilibrium, said method further comprising the step of establishing a nonequilibrium population in the occupation of the electron energy levels in said valence and conduction bands by supplying energy to move electrons from filled levels in said valence band to unfilled levels in said conduction band, the lattice temperature of the semiconductor being maintained at a value low enough to enablE the semiconductor to sustain at least two separate inverted electron populations in energy level band valleys having different values of vector pseudomomentum k, said method further comprising the step of applying a stress to the semiconductor, the stress being one that lifts the multi-valley degeneracy and being of sufficient strength that intervalley electronic transitions combined with the generation of corresponding momentum conserving phonons take place.
Claim 2
Independent Claim
208 words
A method of generating phonons, that comprises, providing a body of semiconductor having a multi-valley energy level band structure, that is, a semiconductor whose electron energy level band extrema are not at k 0, where k is vector pseudomomentum, so that degenerate valleys result from symmetry, said semiconductor having a conduction band of electron energy levels and a valence band of electron energy levels, said conduction band including unfilled levels and said valence band including filled levels in a condition of thermal equilibrium, said method further comprising the step of establishing a nonequilibrium population in the occupation of the electron energy levels in said valence and conduction bands by supplying energy to move electrons from filled levels in said valence band to unfilled levels in said conduction band, the lattice temperature of the semiconductor being maintained at a value low enough to enablE the semiconductor to sustain at least two separate inverted electron populations in energy level band valleys having different values of vector pseudomomentum k, said method further comprising the step of applying a stress to the semiconductor, the stress being one that lifts the multi-valley degeneracy and being of sufficient strength that intervalley electronic transitions combined with the generation of corresponding momentum conserving phonons take place.
Claim 3
Dependent Claim
49 words
A method as claimed in claim 1 and in which the stress is varied in at least one of direction, magnitude and time to alter the extent to which the multi-valley degeneracy is lifted, thereby to change the amplitude and, frequency of the phonons associated with the intervalley transitions.
Claim 4
Dependent Claim
16 words
A method as claimed in claim 1 and in which the stress is a symmetry-breaking stress.
Claim 5
Dependent Claim
22 words
A method as claimed in claim 1 and in which the population inversion is achieved by operating the semiconductor as a diode.
Claim 6
Dependent Claim
19 words
A method as claimed in claim 1 and in which the electron population inversion is effected by optical pumping.
Claim 7
Dependent Claim
38 words
A method as claimed in claim 1 and in which the electron population inversion is effected by passing an electron beam through the semiconductor, energy being extracted from the beam to create negative electron temperature within the semi-conductor.
Claim 8
Dependent Claim
17 words
A method as claimed in claim 1 and in which the stress applied is a shear stress.
Claim 9
Dependent Claim
190 words
Apparatus for generating phonons, that comprises, a multi-valley semiconductor, that is, a semiconductor whose band extrema are not at k 0, where k is vector pseudomomentum, so that degenerate valleys result from symmetry, said semiconductor having a conduction band of electron energy levels and a valence band of electron energy levels, said conduction band including unfilled levels and said valence band including filled levels in a condition of thermal equilibrium, means for establishing an inverted population in the occupation of the electronic energy levels of the valence and conduction bands of the semiconductor by supplying energy to move electrons from filled levels in said valence band to unfilled levels in said conduction band, means for maintaining the lattice temperature of the semiconductor at a value low enough to enable the semiconductor material to sustain at least two separate inverted electron populations in energy level band valleys having different values of vector psuedomomentum k, and means for applying a stress to the semiconductor, the stress being one that lifts the multi-valley degeneracy and of sufficient strength that intervalley electronic transitions combined with the generation of corresponding momentum conserving phonons take place.
Claim 10
Dependent Claim
190 words
Apparatus for generating phonons, that comprises, a multi-valley semiconductor, that is, a semiconductor whose band extrema are not at k 0, where k is vector pseudomomentum, so that degenerate valleys result from symmetry, said semiconductor having a conduction band of electron energy levels and a valence band of electron energy levels, said conduction band including unfilled levels and said valence band including filled levels in a condition of thermal equilibrium, means for establishing an inverted population in the occupation of the electronic energy levels of the valence and conduction bands of the semiconductor by supplying energy to move electrons from filled levels in said valence band to unfilled levels in said conduction band, means for maintaining the lattice temperature of the semiconductor at a value low enough to enable the semiconductor material to sustain at least two separate inverted electron populations in energy level band valleys having different values of vector psuedomomentum k, and means for applying a stress to the semiconductor, the stress being one that lifts the multi-valley degeneracy and of sufficient strength that intervalley electronic transitions combined with the generation of corresponding momentum conserving phonons take place.
Claim 11
Dependent Claim
190 words
Apparatus for generating phonons, that comprises, a multivalley semiconductor, that is, a semiconductor whose band extrema are not at k 0, where k is vector pseudomomentum, so that degenerate valleys result from symmetry, said semiconductor having a conduction band of electron energy levels and a valence band of electron energy levels, said conduction band including unfilled levels and said valence band including filled levels in a condition of thermal equilibrium, means for establishing an inverted population in the occupation of the electronic energy levels of the valence and conduction bands of the semiconductor by supplying energy to move electrons from filled levels in said valence band to unfilled levels in said conduction band, means for maintaining the lattice temperature of the semiconductor at a value low enough to enable the semiconductor material to sustain at least two separate inverted electron populations in energy level band valleys having different values of vector psuedomomentum k, and means for applying a stress to the semiconductor, the stress being one that lifts the multi-valley degeneracy and of sufficient strength that intervalley electronic transitions combined with the generation of corresponding momentum conserving phonons take place.
Claim 12
Dependent Claim
190 words
Apparatus for generating phonons, that comprises, a multivalley semiconductor, that is, a semiconductor whose band extrema are not at k 0, where k is vector pseudomomentum, so that degenerate valleys result from symmetry, said semiconductor having a conduction band of electron energy levels and a valence band of electron energy levels, said conduction band including unfilled levels and said valence band including filled levels in a condition of thermal equilibrium, means for establishing an inverted population in the occupation of the electronic energy levels of the valence and conduction bands of the semiconductor by supplying energy to move electrons from filled levels in said valence band to unfilled levels in said conduction band, means for maintaining the lattice temperature of the semiconductor at a value low enough to enable the semiconductor material to sustain at least two separate inverted electron populations in energy level band valleys having different values of vector psuedomomentum k, and means for applying a stress to the semiconductor, the stress being one that lifts the multi-valley degeneracy and of sufficient strength that intervalley electronic transitions combined with the generation of corresponding momentum conserving phonons take place.
Claim 13
Dependent Claim
40 words
Apparatus as claimed in claim 8 and in which an acoustic resonant cavity is established wholely within the semiconductor and has reflective faces that are parallel and planar to provide reflection surfaces to enable establishment of stimulated emission of phonons.
Claim 14
Dependent Claim
26 words
Apparatus as claimed in claim 8 and in which the semiconductor is selected from the semiconductor group consisting of lead telluride, lead sulphide and lead selenide.
Claim 15
Dependent Claim
20 words
Apparatus as claimed in claim 9 and in which external reflectors form at least part of the acoustic resonant cavity.
Claim 16
Dependent Claim
43 words
Apparatus as claimed in claim 8 and in which means is provided for varying the applied stress in at least one of direction, magnitude, and time thereby to change the amplitude or frequency or combination of amplitude and frequency of the emitted phonons.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-10 | 1978-09-09 | 1979-03-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-10 | 1982-09-09 | 1983-03-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-10 | 1986-09-09 | 1987-03-11 | $7700.00 | Window Closed / Lapsed |