Browsing by Author "Huang, TC"

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A new type of saturable Bragg reflector with record-low saturation fluence and broad tuning range
(1998)
Shieh, JM
;
Huang, TC
;
Huang, KF
;
Wang, CL
;
Pan, CL
The saturation fluence for a strained triple-quantum-well saturable Bragg reflector was as low as 12 mu J/cm(2) Self-starting femtosecond pulses tunable from 768 to 804nm was realized.
Broadly tunable self-starting passively mode-locked Ti : sapphire laser with triple-strained quantum-well saturable Bragg reflector
(1998-11-01)
Shieh, JM
;
Huang, TC
;
Huang, KF
;
Wang, CL
;
Pan, CL
We demonstrate broadband mode-locking of femtosecond Ti:sapphire lasers with a new type of saturable Bragg reflector (SBR). Triple-strained quantum wells with separate and sequential bandgaps were used as the absorbing layer. The saturation fluence was as low as 7 mu J/cm(2). Self-starting sub-100 fs pulses tunable from 768 to 804 nm were generated in a standard X-folded cavity without intracavity tight focusing on the SBR or temperature tuning. The threshold fluence for self-starting mode-locking was 1 mu J/cm(2). (C) 1998 Elsevier Science B.V. All rights reserved.
Broadly tunable self-starting passively mode-locked Ti : sapphire laser with triple-strained quantum-well saturable Bragg reflector
(1998-11-01)
Shieh, JM
;
Huang, TC
;
Huang, KF
;
Wang, CL
;
Pan, CL
We demonstrate broadband mode-locking of femtosecond Ti:sapphire lasers with a new type of saturable Bragg reflector (SBR). Triple-strained quantum wells with separate and sequential bandgaps were used as the absorbing layer. The saturation fluence was as low as 7 mu J/cm(2). Self-starting sub-100 fs pulses tunable from 768 to 804 nm were generated in a standard X-folded cavity without intracavity tight focusing on the SBR or temperature tuning. The threshold fluence for self-starting mode-locking was 1 mu J/cm(2). (C) 1998 Elsevier Science B.V. All rights reserved.
Critical point energy as a function of electric field determined by electroreflectance of surface-intrinsic-n(+) type doped GaAs
(2004-11-01)
Chen, YS
;
Wu, KS
;
Wang, DP
;
Huang, KF
;
Huang, TC
Electroreflectance of surface-intrinsic-n(+) type doped GaAs has been measured over a various biased voltage. The spectra have exhibited many Franz-Keldysh oscillations (FKOs) above band gap energy E-g. The electric field F and critical point energy E-c can be determined from the slope and intercept of FKOs fitting. Hence, we can obtain E-c as a function of F. In most of previous works, E-c is taken as E-g. However, it was found that E-c increases with F in this work. In order to explain this, the gain of energy of electron and hole in F was discussed. (C) 2004 American Institute of Physics.
Determination of built-in field by applying fast Fourier transform to the photoreflectance of surface-intrinsic n(+)-type doped GaAs
(1999-01-18)
Wang, DP
;
Wang, KR
;
Huang, KF
;
Huang, TC
;
Chu, AK
Photoreflectance spectroscopy of surface-intrinsic n(+)-doped (s-i-n(+)) GaAs has been measured at various power densities (P-pu) of a pump beam. Many Franz-Keldysh oscillations (FKOs) were observed above the band-gap energy, which will enable the electric-field strength (F) to be determined from the periods of the FKOs. Field F thus obtained is subject to photovoltaic effects. In order to reduce the photovoltaic effects from the pump beam, P-pu was kept below 10 mu W/cm(2) in the previous experiments. Here, we demonstrate that the built-in field can be determined at a larger P-pu by using fast Fourier transform techniques. (C) 1999 American Institute of Physics. [S0003-6951(99)02803-X].
Effect of modulating field on photoreflectance simulated by electroreflectance
(1999-04-01)
Chiou, SJ
;
Sung, YG
;
Wang, DP
;
Huang, KF
;
Huang, TC
Photoreflectance (PR) of surface-intrinsic- n(+) (s-i-n(+)) type doped GaAs has been simulated by electroreflectance (ER). The simulated spectra of the s-i-n(+) sample have exhibited many Franz-Keldysh oscillations, which enable the electric field (F) to be determined. It is known that F's determined from PR are subjected to photovoltaic effect and the measured F is close to F-bi -delta F/2 when the modulating field, delta F much less than F-bi, where F-bi is the built- in field of the sample and delta F is the modulating field. In this work, we have investigated the relation between the measured F and delta F not only for the region where delta F much less than F bi holds, but also for a whole range of delta F. In order to determine the magnitude of dF, we have used ER to simulate PR, that is, the measurements of ER under a forward bias, which is set to be equal to delta F/2. (C) 1999 American Institute of Physics. [S0021-8979(99)01906-4].
Effects of polarization on electroreflectance spectroscopy of surface-intrinsic n(+)-type doped GaAs
(2002-01-01)
Sung, YG
;
Chiou, SJ
;
Wang, DP
;
Lu, YT
;
Huang, KF
The electroreflectance (ER) spectra of a surface-intrinsic n(+)-type doped (100) GaAs have been measured at various polarization angles of the probe beam. Several Franz-Keldysh oscillations were observed above the band-gap energy, thus enabling heavy- and light-hole transitions to be separated by the application of the fast Fourier transform to the ER spectra. From this, the ratios of the amplitudes of the light- to heavy-hole transitions versus angle of polarization were obtained. At a large incident angle (80 degrees), the strength of the field of the probe beam in the normal direction of the sample (F(z)) was varied from zero to a larger component. It was found that the ratios increased with increasing F(z) which is consistent with the theory that the light-hole transition becomes more enhanced with z-polarized light. (C) 2002 American Institute of Physics.
Electroreflectance of surface-intrinsic- n(+)-type doped GaAs
(1997-09-15)
Wang, DP
;
Huang, KM
;
Shen, TL
;
Huang, KF
;
Huang, TC
The electroreflectance spectra of surface-intrinsic-n(+)-type-doped GaAs were measured at various bias voltages (V-bias). Results revealed many Franz-Keldysh oscillations (FKOs) above the band-gap energy, which have been attributed to a uniform electric field (F) in the undoped layer below the surface. However, there has been no other evidence for the uniformity of F in the undoped layer. Since it is known that F can be deduced from the periods of the FKOs, the relations between F and V-bias can, thereby, be obtained. The nearly linear relation, thus found, confirms the existence of a nearly uniform field in the undoped layer. From the plot of F against V-bias,the Values of the thickness of the undoped layer and the barrier height can also be evaluated. (C) 1997 American Institute of Physics.
Electroreflectance of surface-intrinsic- n(+)-type doped GaAs
(1997-09-15)
Wang, DP
;
Huang, KM
;
Shen, TL
;
Huang, KF
;
Huang, TC
The electroreflectance spectra of surface-intrinsic-n(+)-type-doped GaAs were measured at various bias voltages (V-bias). Results revealed many Franz-Keldysh oscillations (FKOs) above the band-gap energy, which have been attributed to a uniform electric field (F) in the undoped layer below the surface. However, there has been no other evidence for the uniformity of F in the undoped layer. Since it is known that F can be deduced from the periods of the FKOs, the relations between F and V-bias can, thereby, be obtained. The nearly linear relation, thus found, confirms the existence of a nearly uniform field in the undoped layer. From the plot of F against V-bias,the Values of the thickness of the undoped layer and the barrier height can also be evaluated. (C) 1997 American Institute of Physics.
Electroreflectance of surface-intrinsic-n(+)-type-doped GaAs by using a large modulating field
(2003-12-01)
Lin, YC
;
Wang, KQ
;
Wang, DP
;
Huang, KF
;
Huang, TC
It is known that electroreflectance of surface-intrinsic-n(+)-type-doped GaAs has exhibited many Franz-Keldysh oscillations to enable the application of fast Fourier transform to separate the heavy- and light-hole transitions. However, each peak still contains two components, which belong to F+deltaF/2 and F-deltaF/2, respectively, where F is the electric-field strength in the undoped layer and deltaF is the modulating field of applied ac voltage (V-ac). In order to resolve the heavy- and light-hole transitions, deltaF was kept much smaller than F in the previous works. In this work, we have used a larger V-ac and, hence, a larger deltaF, to further separate the peaks. The peaks can be divided into two groups which belong to F+deltaF/2 and F-deltaF/2, respectively. The peak belonging to the heavy-hole transition and F-deltaF/2 can be singled out to compare with the Airy function theory. (C) 2003 American Institute of Physics.
Evaluation of modulating field of photoreflectance of surface-intrinsic-n(+) type doped GaAs by using photoinduced voltage
(2002-04-01)
Lee, WY
;
Chien, JY
;
Wang, DP
;
Huang, KF
;
Huang, TC
Photoreflectance (PR) of surface-intrinsic-n(+) type doped GaAs has been measured for various power densities of pump laser. The spectra exhibited many Franz-Keldysh oscillations, whereby the strength of electric field F in the undoped layer can be determined. The thus obtained Fs are subject to photovoltaic effect and are less than built-in field F-bi. In the previous work we have obtained the relation Fapproximate toF(bi)-deltaF/2 when deltaF
Temperature dependence of Fermi level obtained by electroreflectance spectroscopy of undoped n(+)-type doped GaAs
(1997-12-29)
Huang, KM
;
Wang, KL
;
Wang, DP
;
Huang, KF
;
Huang, TC
The electroreflectance (ER) spectra of an undoped n(+)-type doped GaAs have been measured over a range of temperature from 25 to 400 K. Many Franz-Keldysh oscillations were observed above the band-gap energy, which enabled the electric field strength and, hence, also the Fermi level to be determined. The photovoltaic effect is shown to be negligible, even at the low temperature. The experiment shows that the Fermi level decreases with increasing temperature and has almost the same temperature dependence as the energy gap. It is pinned at about 0.63 of energy gap below the conduction band. (C) 1997 American Institute of Physics.
The effects of the magnitude of the modulation field on electroreflectance spectroscopy of undoped-n(+) type doped GaAs
(1998-01-01)
Wang, DP
;
Huang, KM
;
Shen, TL
;
Huang, KF
;
Huang, TC
The electroreflectance (ER) spectra of an undoped-n(+) type doped GaAs has been measured at various amplitudes of modulating fields (delta F). Many Franz-Keldysh oscillations were observed above the band gap energy, thus enabling the electric field (F) in the undoped layer to be determined. The F is obtained by applying fast Fourier transformation to the ER spectra. When delta F is small, the power spectrum can be clearly resolved into two peaks, which corresponds to heavy- and light-hole transitions. When delta F is less than similar to 1/8 of the built-in field (F(bi)similar to 77 420 V/cm), the F deduced from the ER is almost independent of delta F. However, when larger than this, F is increased with delta F. Also, when delta F is increased to larger than similar to 1/8 of F-bi, a shoulder appears on the right side of the heavy-hole peak of the power spectrum. The separation between the main peak and the shoulder of the heavy-hole peak becomes wider as delta F becomes larger. (C) 1998 American Institute of Physics.