Browsing by Author "HUANG, YM"

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ENHANCEMENT OF THE STARK-EFFECT IN ALINAS/GAINAS COUPLED QUANTUM-WELLS AND THEIR APPLICATIONS TO TUNABLE MIDINFRARED PHOTODETECTORS
(1994-09-01)
HUANG, YM
;
LIEN, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A tunable midinfrared photodetector using 1 --> 4 intersubband Stark shift in the four-level AlInAs/GaInAs coupled quantum wells (CQWs) is proposed. The operation of this device is based on the infrared absorption by the electrons in the ground state transited from the ground-state subband E1 of the CQWs to the third-excited-state subband E4. A large variation of eigenenergy spacing DELTAE41 between E1 and E4 under an applied electric field can be achieved for the proposed AlInAs/GaInAs CQW system. Since the infrared radiation is absorbed via the intersubband resonance absorption (homegaBAR = E4-E1), the detected infrared wavelength can be tuned by the spacing DELTAE41 which can be adjusted by an applied electric field. The tunability of these AlInAs/GaInAs CQWs have been studied theoretically. Based on theoretical calculations, tuning ranges from 3 to 3.9 and 2.9 to 4.2 mum are predicted for the proposed asymmetric CQW structure and compositionally asymmetric COW structure, respectively. This tuning capability is achieved by varying the applied electric field in the 90 to -90 kV/cm range.
ENHANCEMENT OF THE STARK-EFFECT IN ALINAS/GAINAS COUPLED QUANTUM-WELLS AND THEIR APPLICATIONS TO TUNABLE MIDINFRARED PHOTODETECTORS
(1994-09-01)
HUANG, YM
;
LIEN, CH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A tunable midinfrared photodetector using 1 --> 4 intersubband Stark shift in the four-level AlInAs/GaInAs coupled quantum wells (CQWs) is proposed. The operation of this device is based on the infrared absorption by the electrons in the ground state transited from the ground-state subband E1 of the CQWs to the third-excited-state subband E4. A large variation of eigenenergy spacing DELTAE41 between E1 and E4 under an applied electric field can be achieved for the proposed AlInAs/GaInAs CQW system. Since the infrared radiation is absorbed via the intersubband resonance absorption (homegaBAR = E4-E1), the detected infrared wavelength can be tuned by the spacing DELTAE41 which can be adjusted by an applied electric field. The tunability of these AlInAs/GaInAs CQWs have been studied theoretically. Based on theoretical calculations, tuning ranges from 3 to 3.9 and 2.9 to 4.2 mum are predicted for the proposed asymmetric CQW structure and compositionally asymmetric COW structure, respectively. This tuning capability is achieved by varying the applied electric field in the 90 to -90 kV/cm range.
THE DOUBLE RESONANT ENHANCEMENT OF OPTICAL 2ND-HARMONIC SUSCEPTIBILITY IN THE COMPOSITIONALLY ASYMMETRIC COUPLED-QUANTUM-WELL
(1994-02-15)
LIEN, CS
;
HUANG, YM
;
LEI, TF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The second harmonic suceptibility due to the intersubband transitions in the three-level GaAs/AlxGa1-xAs/AlyGa1-yAs compositionally asymmetric coupled quantum well (CACQW) under the influence of the applied electric field is investigated theoretically. The subband eigenenergy E(n) of the CACQOW structure could he designed to form an equally spaced energy-level ladder. Since the eigenenergy spacing could be designed to resonate with the pumping source, the second harmonic susceptibility could be greatly enhanced through the double resonance. Based on the theoretical calculations, the second harmonic susceptibility as high as 220 nm/V can be achieved for the CACQW. This is a more than three orders of magnitude enhancement as compared to that of the bulk GaAs. In addition to the design of CACQW structure, the double resonance can also be achieved by biasing the CACQW under a proper electric field. The extinguishment of the second order nonlinear optical effect by the applied electric field has also been studied. This phenomenon is attributed to the symmetry restoration of envelope wave functions of the CACQW structures under the quenching electric field C(off). A simple physical model to estimate the C(off) has also been developed.
THE ENHANCED STARK EFFECTS OF COUPLED QUANTUM-WELLS AND THEIR APPLICATION TO TUNABLE IR PHOTODETECTORS
(1993-08-15)
HUANG, YM
;
LIEN, CH
;
LEI, TF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A tunable asymmetric coupled quantum well far-infrared photodetector is proposed in this paper. The basic asymmetric coupled quantum wells are composed of two quantum wells separated by a thin barrier. In this way, the electron in each well interacts strongly with other electrons to achieve a large Stark tuning effect. The eigenenergies and the wave functions of the quantum-well structures are solved by the self-consistent method, and the effect of the exchange interaction on the ground-state subband has also been taken into account. The absorption coefficient is evaluated by the density-of-states formalism. Based on theoretical calculations, tuning ranges from 8.2 to 11.3 mum and 7.8 to 10.5 mum are predicted for the proposed asymmetric coupled-quantum-well structure and high-low coupled-quantum-well structure, respectively. This tuning capability is achieved by varying the applied electric field in the 20-90-kV/cm range.
THE ENHANCEMENT OF OPTICAL 3RD HARMONIC SUSCEPTIBILITY IN A PARABOLIC QUANTUM-WELL BY TRIPLE-RESONANCE
(1994-03-15)
HUANG, YM
;
LIEN, CS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The third harmonic susceptibility for the finite parabolic quantum well (PQW) is studied theoretically. An important feature of the finite PQW is that the subband eigenenergies E(n) form an equally spaced energy-level ladder. Since the eigenenergy spacing hBARomega0 can be designed to resonate with the pumping source, the third harmonic susceptibility can be greatly enhanced through the triple resonance' A third harmonic susceptibility as high as 2000 (mm/V)2 could be achieved for the finite parabolic quantum well structure. This is a more than six orders of magnitude enhancement as compared to that of the bulk GaAs.
TRIPLY RESONANT ENHANCEMENT OF 3RD-ORDER NONLINEAR-OPTICAL SUSCEPTIBILITY IN COMPOSITIONALLY ASYMMETRIC COUPLED QUANTUM-WELLS
(1994-07-15)
LIEN, CS
;
HUANG, YM
;
WANG, JF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The third-order nonlinear optical susceptibility chi(3)(3omega) due to the intersubband transitions in the four-level AlInAs/GaInAs compositionally asymmetric coupled quantum well (CACQW) is investigated theoretically. The subband eigenenergy E(n) of the CACQW structure could be designed to form an equally spaced energy-level ladder. Since the eigenenergy spacing could be designed to resonate with the pumping source, the third-order nonlinear optical susceptibility could be greatly enhanced through the triple resonance. Based on the theoretical calculations, a magnitude of chi(3)(3omega) as high as 2.2 X 10(5) (nm/V)2 can be achieved for the CACQW structure. This is a more than eight orders of magnitude enhancement as compared to that of the bulk value in GaAs. In addition to the design of CACQW structure, the triple resonance can also be achieved by biasing the CACQW under a proper electric field due to the large Stark effect of the CACQW structure.