Optical: systems and elements – Optical modulator – Light wave temporal modulation
Patent
1996-01-11
1998-03-03
Nelms, David C.
Optical: systems and elements
Optical modulator
Light wave temporal modulation
G02F 103
Patent
active
057241740
ABSTRACT:
The present invention is an electro-optical modulator having (a) a first semiconductor layer and a second semiconductor layer; (b) a first quantum well layer having a conduction band minimum at an optically active point (typically the L point or the X point), disposed between the first and second semiconductor layers; (c) a second quantum well layer having a conduction band minimum at the optically inactive (at normal incidence) .GAMMA. point, disposed between the first and second semiconductor layers; (d) a spacer layer disposed between the first and second quantum well layers, where the spacer layer has a conduction band minimum that is large enough for establishing quantum confinement in the first quantum well layer at the optically active point and in the second quantum well layer at the .GAMMA. point, but small enough to allow tunnelling between the two layers on a time scale consistent with the desired switching response time. The invention also has some controllable means for applying an electric field. The invention can produce both intensity and phase changes, and may be used in a Fabry-Perot device to achieve greater modulation for a given active region thickness.
REFERENCES:
patent: 5225692 (1993-07-01), Takeuchi et al.
patent: 5521398 (1996-05-01), Pelekanos et al.
Xie et al., "Infrared electroabsorption modulation at normal incidence in ymmetrically stepped AlSb/InAs/Ga/Sb/AlSb quantum wells", J. Applied Physics 76 (1) 92-96 (Jul. 1, 1994).
Xie et al., "Enchancement of intersubband Stark effects in L-valley step quantum wells for infrared modulcation and voltage tunable detection", J. Applied Physics 74 (2) 1195-98 (Jul. 15, 1993).
Xie et al., "Normal incidence infrared modulator using direct-indirect transitions in GaSb quantum wells", Applied Physics Letters 63 (6) 776-78 (Aug. 9, 1993).
Meyer et al., "Infrared electro-optical modulators based on field-induced Gamma-L intervalley transfer", Applied Physics Letters 67 (19) 2756-58 (Nov. 6, 1995).
Bartoli Filbert
Hoffman Craig A.
Meyer Jerry R.
Karasek John J.
McDonnell Thomas E.
Nelms David C.
Robbins Thomas
The United States of America as represented by the Secretary of
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