The basic design principles and parameters of GaAs/AlGaAs quantum well infrared photodetectors (QWIP) are reviewed.Furthermore new research directions,devices and applications suited for QWIPs are discussed.These incl...The basic design principles and parameters of GaAs/AlGaAs quantum well infrared photodetectors (QWIP) are reviewed.Furthermore new research directions,devices and applications suited for QWIPs are discussed.These include monolithic integration of QWIPs with GaAs based electronic and optoelectronic devices,high frequency and high speed QWIPs and applications,multicolor and multispectral detectors,and p-type QWIPs.展开更多
For eventually providing terahertz science with compact and convenient devices,terahertz (1～10THz) quantum-well photodetectors and quantum-cascade lasers are investigated.The design and projected detector performance...For eventually providing terahertz science with compact and convenient devices,terahertz (1～10THz) quantum-well photodetectors and quantum-cascade lasers are investigated.The design and projected detector performance are presented together with experimental results for several test devices,all working at photon energies below and around optical phonons.Background limited infrared performance (BLIP) operations are observed for all samples (three in total),designed for different wavelengths.BLIP temperatures of 17,13,and 12K are achieved for peak detection frequencies of 9.7THz(31μm),5.4THz(56μm),and 3.2THz(93μm),respectively.A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is studied.The δ-doping density for each period varies from 3.2×1010 to 4.8×1010cm-2.We observe that the lasing threshold current density increases monotonically with doping concentration.Moreover,the measurements for devices with different cavity lengths provide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically.Interestingly the observed maximum lasing temperature is best at a doping density of 3.6×1010cm-2.展开更多
We report on a study of terahertz(THz) generation using implanted In Ga As photomixers and multi-wavelength quantum dot lasers. We carry out In Ga As materials growth, optical characterization, device design and fabri...We report on a study of terahertz(THz) generation using implanted In Ga As photomixers and multi-wavelength quantum dot lasers. We carry out In Ga As materials growth, optical characterization, device design and fabrication, and photomixing experiments. This approach is capable of generating a comb of electromagnetic radiation from microwave to terahertz. For shortening photomixer carrier lifetime, we employ proton implantation into an epitaxial layer of lattice matched In Ga As grown on InP. Under a 1.55 μm multimode In GaAs/In GaAsP quantum dot laser excitation, a frequency comb with a constant frequency spacing of 50 GHz generated on the photomixer is measured, which corresponds to the beats of the laser longitudinal modes. The measurement is performed with a Fourier transform infrared spectrometer. This approach affords a convenient method to achieve a broadband multi-peak coherent THz source.展开更多
In order to verify the properties of the light propagating through a gradient-index （GRIN） fibre probe for optical coherence tomography （OCT）, numerical simulation using the optical software GLAD is carried out. F...In order to verify the properties of the light propagating through a gradient-index （GRIN） fibre probe for optical coherence tomography （OCT）, numerical simulation using the optical software GLAD is carried out. Firstly, the model of the GRIN fibre probe is presented, which is consisted of a single mode fibre （SMF）, a no-core fibre （NCF）, a GRIN fibre lens and an air path. Then, the software GLAD is adopted to numerically investigate how the lengths of the NCF and the GRIN fibre lens influence the performance of the Gaussian beam focusing through the GRIN fibre probe. The simulation results are well consistent with the experimental ones, showing that the GLAD based numerical simulation technique is an intuitive and effective tool for the verification of the properties of the light propagation. In this paper, we find that on the conditions of a constant GRIN fibre lens length of 0.1 mm and an NCF length of 0.36 mm, the working distance of the probe will be 0.75 mm and the focus spot size is 32 μm.展开更多
William(familiarly known as Bill by all his colleagues) Yen's life-long scientific interest in the magnetic properties of rutile structured antiferromagnetic materials(AFMs) began with his involvement in the disco...William(familiarly known as Bill by all his colleagues) Yen's life-long scientific interest in the magnetic properties of rutile structured antiferromagnetic materials(AFMs) began with his involvement in the discovery in 1965 of the magnon sidebands of MnF2 in optical absorption[1].A basic outline of this discovery is given elsewhere in this special issue of the Chinese Journal of Luminescence[2].A narrative discussion of events leading to this discovery appears in a contribution written by Bill and Robert White for a special edition of Low Temperature Physics on Antiferromagnetism[3].A quote from that remembrance highlights a quality that remained with Bill throughout his career: "The identification of these sidebands by a pair of young students and two post-docs illustrates how serendipity,a touch of good luck and reckless youthful enthusiasm often plays a role in scientific discovery".Bill's forever youthful enthusiasm coupled with creative insights into current research questions led to numerous pioneering discoveries throughout his career.This paper reviews Bill's contributions to developing techniques to exploit dichroism to study the magnetic properties of AFMs.Bill's publications in this area span more than 30 years,from 1971 to 2004.展开更多
In swept-source optical coherence tomography(SSOCT),the swept-source stimulates system by a series of wavelengths in time sequence;a photo detector then collects all reflected/backscattered light from testing sample a...In swept-source optical coherence tomography(SSOCT),the swept-source stimulates system by a series of wavelengths in time sequence;a photo detector then collects all reflected/backscattered light from testing sample as the components of Fourier series.Due to the nature of the SSOCT,the processing in spectral domain can merge multiple swept-sources with different central wavelengths,which greatly increases the resolution of the OCT imaging.In the wavelength probing OCT,a standard broadband SSOCT system is used to extract the internal structure of the sample,and another narrow band light can be used to probe the spectral feature of the sample at the probing wavelength.展开更多
Our latest research results on GaAs-A1GaAs multiple quantum well spatial light modulators are presented. The thickness uniformity of the epitaxial layers across the 3-inch wafer grown by our molecular beam epitaxy is ...Our latest research results on GaAs-A1GaAs multiple quantum well spatial light modulators are presented. The thickness uniformity of the epitaxial layers across the 3-inch wafer grown by our molecular beam epitaxy is better than 0.1% and the variation of cavity resonance wavelength within the wafer is only 0.9 nm. A contrast ratio （CR） of 102 by varying bias voltage from 0 to 6.7 V is achieved after fine tuning the cavity by etching an adjust layer. Both theoretical and experimental results demonstrate that incorporating an adjust layer is an effective tuning method for obtaining high CR.展开更多
We demonstrate a novel method for indium bump fabrication on a small CMOS circuit chip that is to be flip-chip bonded with a GaAs/A1GaAs multiple quantum well spatial light modulator. A chip holder with a via hole is ...We demonstrate a novel method for indium bump fabrication on a small CMOS circuit chip that is to be flip-chip bonded with a GaAs/A1GaAs multiple quantum well spatial light modulator. A chip holder with a via hole is used to coat the photoresist for indium bump lift-off. The 1000 μm-wide photoresist edge bead around the circuit chip can be reduced to less than 500 μm, which ensures the integrity of the indium bump array. 64 - 64 indium arrays with 20 μm-high, 30 μm-diameter bumps are successfully formed on a 5 - 6.5 mm^2 CMOS chip.展开更多
Polarized light microscopy （PLM） is used to image individual single-walled carbon nanotubes （SWNTs） suspended in air across a slit opening. The imaging contrast relies on the strong optical anisotropy typical of S...Polarized light microscopy （PLM） is used to image individual single-walled carbon nanotubes （SWNTs） suspended in air across a slit opening. The imaging contrast relies on the strong optical anisotropy typical of SWNTs. We combine PLM with a tunable light source to enable hyperspectral excitation spectroscopy and nanotube chirality assignment. Comparison with fluorescence microscopy and spectroscopy confirms the assignment made with PLM. This represents a versatile new approach to imaging SWNTs and related structures.展开更多
The dynamics of the chemical vapor deposition(CVD)of single-walled carbon nanotubes(SWNTs)is extracted experimentally using in situ Raman spectroscopy.Nanotubes are grown using a thinlm cobalt catalyst and an ethanol...The dynamics of the chemical vapor deposition(CVD)of single-walled carbon nanotubes(SWNTs)is extracted experimentally using in situ Raman spectroscopy.Nanotubes are grown using a thinlm cobalt catalyst and an ethanol precursor in a miniature hot walled reactor with optical access.Raman spectra at room temperature and at the growth temperature are compared for two growth temperatures.The evolution of the G-band,D-band,and radial breathing mode(RBM)is tracked at the growth temperature with time resolution of a few seconds.There are three identifiable phases in the evolution of the Raman signal intensity:an initial exponential increasing phase,a linear growth phase,and a saturation phase.In situ optical spectroscopy thus enables the study of nucleation,steady growth,and deactivation processes to be investigated separately in real time.The evolution curves for all bands(G,D,and RBM),when scaled,collapse onto the same curve,to within experimental uncertainty.展开更多
文摘The basic design principles and parameters of GaAs/AlGaAs quantum well infrared photodetectors (QWIP) are reviewed.Furthermore new research directions,devices and applications suited for QWIPs are discussed.These include monolithic integration of QWIPs with GaAs based electronic and optoelectronic devices,high frequency and high speed QWIPs and applications,multicolor and multispectral detectors,and p-type QWIPs.
文摘For eventually providing terahertz science with compact and convenient devices,terahertz (1～10THz) quantum-well photodetectors and quantum-cascade lasers are investigated.The design and projected detector performance are presented together with experimental results for several test devices,all working at photon energies below and around optical phonons.Background limited infrared performance (BLIP) operations are observed for all samples (three in total),designed for different wavelengths.BLIP temperatures of 17,13,and 12K are achieved for peak detection frequencies of 9.7THz(31μm),5.4THz(56μm),and 3.2THz(93μm),respectively.A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is studied.The δ-doping density for each period varies from 3.2×1010 to 4.8×1010cm-2.We observe that the lasing threshold current density increases monotonically with doping concentration.Moreover,the measurements for devices with different cavity lengths provide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically.Interestingly the observed maximum lasing temperature is best at a doping density of 3.6×1010cm-2.
基金supported in part by NSERC. HCL thanks the support by the National Ma jor Basic Research Pro jects (2011CB925603)Shanghai Municipal Ma jor Basic Research Pro ject (09DJ1400102)
文摘We report on a study of terahertz(THz) generation using implanted In Ga As photomixers and multi-wavelength quantum dot lasers. We carry out In Ga As materials growth, optical characterization, device design and fabrication, and photomixing experiments. This approach is capable of generating a comb of electromagnetic radiation from microwave to terahertz. For shortening photomixer carrier lifetime, we employ proton implantation into an epitaxial layer of lattice matched In Ga As grown on InP. Under a 1.55 μm multimode In GaAs/In GaAsP quantum dot laser excitation, a frequency comb with a constant frequency spacing of 50 GHz generated on the photomixer is measured, which corresponds to the beats of the laser longitudinal modes. The measurement is performed with a Fourier transform infrared spectrometer. This approach affords a convenient method to achieve a broadband multi-peak coherent THz source.
基金supported by the International Cooperation Project of Shanghai Science and Technology Committee,China(Grant No.09530708700)
文摘In order to verify the properties of the light propagating through a gradient-index （GRIN） fibre probe for optical coherence tomography （OCT）, numerical simulation using the optical software GLAD is carried out. Firstly, the model of the GRIN fibre probe is presented, which is consisted of a single mode fibre （SMF）, a no-core fibre （NCF）, a GRIN fibre lens and an air path. Then, the software GLAD is adopted to numerically investigate how the lengths of the NCF and the GRIN fibre lens influence the performance of the Gaussian beam focusing through the GRIN fibre probe. The simulation results are well consistent with the experimental ones, showing that the GLAD based numerical simulation technique is an intuitive and effective tool for the verification of the properties of the light propagation. In this paper, we find that on the conditions of a constant GRIN fibre lens length of 0.1 mm and an NCF length of 0.36 mm, the working distance of the probe will be 0.75 mm and the focus spot size is 32 μm.
文摘William(familiarly known as Bill by all his colleagues) Yen's life-long scientific interest in the magnetic properties of rutile structured antiferromagnetic materials(AFMs) began with his involvement in the discovery in 1965 of the magnon sidebands of MnF2 in optical absorption[1].A basic outline of this discovery is given elsewhere in this special issue of the Chinese Journal of Luminescence[2].A narrative discussion of events leading to this discovery appears in a contribution written by Bill and Robert White for a special edition of Low Temperature Physics on Antiferromagnetism[3].A quote from that remembrance highlights a quality that remained with Bill throughout his career: "The identification of these sidebands by a pair of young students and two post-docs illustrates how serendipity,a touch of good luck and reckless youthful enthusiasm often plays a role in scientific discovery".Bill's forever youthful enthusiasm coupled with creative insights into current research questions led to numerous pioneering discoveries throughout his career.This paper reviews Bill's contributions to developing techniques to exploit dichroism to study the magnetic properties of AFMs.Bill's publications in this area span more than 30 years,from 1971 to 2004.
文摘In swept-source optical coherence tomography(SSOCT),the swept-source stimulates system by a series of wavelengths in time sequence;a photo detector then collects all reflected/backscattered light from testing sample as the components of Fourier series.Due to the nature of the SSOCT,the processing in spectral domain can merge multiple swept-sources with different central wavelengths,which greatly increases the resolution of the OCT imaging.In the wavelength probing OCT,a standard broadband SSOCT system is used to extract the internal structure of the sample,and another narrow band light can be used to probe the spectral feature of the sample at the probing wavelength.
基金supported by the President Fund of CAS,the International Collaboration Plan for Science and Technology of the Chinese Ministry of Science and Technology(No.2008KR0415)the Suzhou International Cooperation Fund,China(No.SWH0809).
文摘Our latest research results on GaAs-A1GaAs multiple quantum well spatial light modulators are presented. The thickness uniformity of the epitaxial layers across the 3-inch wafer grown by our molecular beam epitaxy is better than 0.1% and the variation of cavity resonance wavelength within the wafer is only 0.9 nm. A contrast ratio （CR） of 102 by varying bias voltage from 0 to 6.7 V is achieved after fine tuning the cavity by etching an adjust layer. Both theoretical and experimental results demonstrate that incorporating an adjust layer is an effective tuning method for obtaining high CR.
文摘We demonstrate a novel method for indium bump fabrication on a small CMOS circuit chip that is to be flip-chip bonded with a GaAs/A1GaAs multiple quantum well spatial light modulator. A chip holder with a via hole is used to coat the photoresist for indium bump lift-off. The 1000 μm-wide photoresist edge bead around the circuit chip can be reduced to less than 500 μm, which ensures the integrity of the indium bump array. 64 - 64 indium arrays with 20 μm-high, 30 μm-diameter bumps are successfully formed on a 5 - 6.5 mm^2 CMOS chip.
文摘Polarized light microscopy （PLM） is used to image individual single-walled carbon nanotubes （SWNTs） suspended in air across a slit opening. The imaging contrast relies on the strong optical anisotropy typical of SWNTs. We combine PLM with a tunable light source to enable hyperspectral excitation spectroscopy and nanotube chirality assignment. Comparison with fluorescence microscopy and spectroscopy confirms the assignment made with PLM. This represents a versatile new approach to imaging SWNTs and related structures.
基金A discovery grant(PF,AL)from Natural Sciences and Engineering Research Council of Canada(NSERC)and a grant(AL)from Le Fonds québécois de la recherche sur la nature et les technologies(FQRNT)are gratefully acknowledged.We are grateful for the ongoing assistance of P.Marshall,Hue Tran,Jeff Fraser and other IMS staff and for preliminary research in this area by Jeffery Bond and Kate Kaminska.We are grateful for the funding of in situ Raman studies via the former JST-CREST"Nanofactory"project led by Yoshikazu Homma
文摘The dynamics of the chemical vapor deposition(CVD)of single-walled carbon nanotubes(SWNTs)is extracted experimentally using in situ Raman spectroscopy.Nanotubes are grown using a thinlm cobalt catalyst and an ethanol precursor in a miniature hot walled reactor with optical access.Raman spectra at room temperature and at the growth temperature are compared for two growth temperatures.The evolution of the G-band,D-band,and radial breathing mode(RBM)is tracked at the growth temperature with time resolution of a few seconds.There are three identifiable phases in the evolution of the Raman signal intensity:an initial exponential increasing phase,a linear growth phase,and a saturation phase.In situ optical spectroscopy thus enables the study of nucleation,steady growth,and deactivation processes to be investigated separately in real time.The evolution curves for all bands(G,D,and RBM),when scaled,collapse onto the same curve,to within experimental uncertainty.
