lianhe li

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GHz Heterodyne generation using Two DFB Mid-IR QCL lasers on a 9μm QWIP

High-Brightness Sources and Light-driven Interactions, 2018

We report the implementation of a heterodyne measurement setup using two DFB Mid-IR QCL lasers on... more We report the implementation of a heterodyne measurement setup using two DFB Mid-IR QCL lasers on a 9µm Quantum Well Infrared Photodetector (QWIP). We present the measurement of the signal-to-noise ratio characterization of the detector thanks to the heterodyne technique and the obtained frequency stability for the QCL in terms of a linewidth inferior to 3MHz at 300 KHz of resolution bandwidth.

Dataset relating to 'On-chip Terahertz Frequency Measurements of Liquids

This dataset includes ASCII data for all figures described in the paper entitled 'On-chip Ter... more

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Ultra-Small Mode Volume Three-Dimensional THz LC Metamaterial

2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2019

Electrically-controlled frequency tuning of terahertz quantum cascade lasers over 190 GHz using a coupled cavity with integrated photonic lattice

Conference or Workshop Item: Kundu, I orcid.org/0000-0002-3564-1903, Dean, P, Valavanis, A orcid.... more Conference or Workshop Item: Kundu, I orcid.org/0000-0002-3564-1903, Dean, P, Valavanis, A orcid.org/0000-0001-5565-0463 et al. (3 more authors) (Accepted: 2017) Electrically-controlled frequency tuning of terahertz quantum cascade lasers over 190 GHz using a coupled cavity with integrated photonic lattice. In: Optical Terahertz Science and Technology (OTST 2017), 02-07 Apr 2017, London, UK. (Unpublished)

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Probing Ultrafast Switch-on Dynamics of Frequency Tuneable Semiconductor Lasers Using Terahertz Time-domain Spectroscopy

2019 IEEE Photonics Society Summer Topical Meeting Series (SUM), 2019

We report measurements of switch-on dynamics, mode competition and frequency selection in a monol... more We report measurements of switch-on dynamics, mode competition and frequency selection in a monolithic frequency-tuneable laser using coherent time-domain sampling of the laser emission. We observe hopping between lasing modes on picosecond-timescales and temporal evolution of transient multi-mode emission into steady-state single mode emission.

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Giant optical nonlinearity interferences in quantum structures

Science Advances, 2019

We bring to light the complex interplay of optical nonlinearities in quantum structures.

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Analysis of Extended Threshold Wavelength Photoresponse in Nonsymmetrical p-GaAs/AlGaAs Heterostructure Photodetectors

IEEE Journal of Selected Topics in Quantum Electronics, 2018

We analyze the extended wavelength photoresponse beyond the standard threshold limit ( / . t 24 1... more We analyze the extended wavelength photoresponse beyond the standard threshold limit ( / . t 24 1 , where is the activation energy) in non-symmetrical p-GaAs/AlGaAs heterostructure photodetectors with a barrier energy offset. We propose that hot-cold hole carrier interactions in the p-GaAs absorber are responsible for the threshold wavelength extension. Experimental results are analyzed by considering a quasi-Fermi distribution of hot holes at a hot hole temperature H T , which is much higher than the lattice temperature L T . The experimental photoresponse is fitted using an escape cone model, modified with a quasi-Fermi level (EquasiF). The simulated results are found to be in good agreement with experimental data, justifying the model used.

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Infinite-Period Density-Matrix Model for Terahertz-Frequency Quantum Cascade Lasers

IEEE Transactions on Terahertz Science and Technology, 2017

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Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers

Nature, 2018

Room temperature operation is mandatory for any optoelectronics technology which aims to provide ... more Room temperature operation is mandatory for any optoelectronics technology which aims to provide low-cost compact systems for widespread applications. In recent years, an important technological effort in this direction has been made in bolometric detection for thermal imaging 1 , which has delivered relatively high sensitivity and video rate performance ( 60 Hz). However, room temperature operation is still a major challenge for semiconductor photodetectors in the 8-12 ´m wavelength band 2 , and all developments for applications such as imaging, environmental remote sensing and laser-based free-space communication 3-5 have therefore had to be realised at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high temperature operation 6,7 . Here, we show that a 9 ´m quantum well infrared photodetector 8 , implemented in a metamaterial made of subwavelength metallic resonators 9-12 , has strongly enhanced performances up to room temperature. This occurs because the photonic collection area is increased with respect to the electrical area for each resonator, thus significantly reducing the dark current of the device 13 . Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature 14,15 , which constrains conventional geometries at cryogenic operation 6 . Finally, the reduced physical area of the device and its increased responsivity allows us to take advantage of the intrinsic high frequency response of the quantum detector 7 at room temperature. By beating two quantum cascade lasers 16 we have measured the heterodyne signal at high frequencies, above 4 GHz. These wide band uncooled detectors shall have therefore a significant impact on technologies such as multichannel coherent Gigabit/s data transfer 17 and high precision molecular spectroscopy 18 .

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Two-dimensional coherent spectroscopy of a THz quantum cascade laser: observation of multiple harmonics

Optics Express, 2017

Two-dimensional spectroscopy is performed on a terahertz (THz) frequency quantum cascade laser (Q... more Two-dimensional spectroscopy is performed on a terahertz (THz) frequency quantum cascade laser (QCL) with two broadband THz pulses. Gain switching is used to amplify the first THz pulse and the second THz pulse is used to probe the system. Fourier transforms are taken with respect to the delay time between the two THz pulses and the sampling time of the THz probe pulse. The two-dimensional spectrum consists of three peaks at ( = 0, t = 0 ), ( = 0 , t = 0 ), and ( = 2 0 , t = 0 ) where 0 denotes the lasing frequency. The peak at = 0 represents the response of the probe to the zero-frequency (rectified) component of the instantaneous intensity and can be used to measure the gain recovery.

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Temperature-dependent modulated reflectance of InAs/InGaAs/GaAs quantum dots-in-a-well infrared photodetectors

Journal of Applied Physics, 2015

We present a photoreflectance (PR) study of multi-layer InAs quantum dot (QD) photodetector struc... more We present a photoreflectance (PR) study of multi-layer InAs quantum dot (QD) photodetector structures, incorporating InGaAs overgrown layers and positioned asymmetrically within GaAs/AlAs quantum wells (QWs). The influence of the back-surface reflections on the QD PR spectra is explained and a temperature-dependent photomodulation mechanism is discussed. The optical interband transitions originating from the QD/QW ground- and excited-states are revealed and their temperature behaviour in the range of 3–300 K is established. In particular, we estimated the activation energy (∼320 meV) of exciton thermal escape from QD to QW bound-states at high temperatures. Furthermore, from the obtained Varshni parameters, a strain-driven partial decomposition of the InGaAs cap layer is determined.

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1.3-μm GaInNAs/GaAs quantum well lasers and photodetectors

SPIE Proceedings, 2001

The growth of GaInNAs/GaAs quantum well (QW) has been investigated by solid-source molecular beam... more The growth of GaInNAs/GaAs quantum well (QW) has been investigated by solid-source molecular beam epitaxy (MBE). N was introduced by a dc-active plasma source. Highest N concentration of 2.6% in GaInNAs/GaAs QW was obtained, corresponding to the photoluminescence peak wavelength of 1.57 (m at 10K. The nitrogen incorporation behavior in MBE growth and the quality improvement of the QW have been studied in detail. 1.3 (m GaInNAs/GaAs SQW laser and MQW resonant-cavity enhanced photodetector have been achieved.

[Expression of EMS1 protein and its clinical significance in laryngeal carcinoma]

Lin chuang er bi yan hou tou jing wai ke za zhi = Journal of clinical otorhinolaryngology, head, and neck surgery, 2009

To investigate the expression of EMS1 in laryngeal carcinoma and its clinical significance. The e... more To investigate the expression of EMS1 in laryngeal carcinoma and its clinical significance. The expression of EMS1 protein was measured in 40 samples of, 40 samples of para carcinoma tissues (which were near to cutting margin of laryngeal carcinoma tissue over 0.5 cm), and 20 samples of normal laryngeal mucosa as controls by Flow Cytometer (Epics-XL II). The quantity and percentage of EMS1 protein expression in laryngeal carcinoma tissues was significantly higher than those in para carcinoma and in normal laryngeal mucosa tissues respectively (P<0.05). There was no significant expression difference between the para carcinoma tissues and normal laryngeal mucosa tissues. There were positive correlation between the expressions of EMS1 protein and metastasis, pathological grade and clinical stage in laryngeal carcinoma. But there were not relationship with patients' clinical classification, tumor size, smoking history, age and sex. The high expression of EMS1 may contribute to th...

On-chip picosecond pulse detection and generation using graphene photoconductive switches

Nano letters, Jan 24, 2015

We report on the use of graphene for room temperature on-chip detection and generation of pulsed ... more We report on the use of graphene for room temperature on-chip detection and generation of pulsed terahertz (THz) frequency radiation, exploiting the fast carrier dynamics of light-generated hot carriers, and compare our results with conventional low-temperature-grown gallium arsenide (LT-GaAs) photoconductive (PC) switches. Coupling of ps-duration pulses from a biased graphene PC switch into Goubau-line waveguides is also demonstrated. A Drude transport model based on the transient photoconductance of graphene is used to describe the mechanism for both detection and generation of THz radiation.

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Comparative optical study of epitaxial InGaAs quantum rods grown with As[sub 2] and As[sub 4] sources

ABSTRACT Photoreflectance and photoluminescence (PL) spectroscopies are used to examine the optic... more ABSTRACT Photoreflectance and photoluminescence (PL) spectroscopies are used to examine the optical properties and electronic structure of InGaAs quantum rods (QRs), embedded within InGaAs quantum well (QW). The nanostructures studied were grown by molecular beam epitaxy using As-2 or As-4 sources. The impact of As source on spectral features associated with interband optical transitions in the QRs and the surrounding QW are demonstrated. A red shift of the QR- and a blue shift of the QW-related optical transitions, along with a significant increase in PL intensity, have been observed if an As4 source is used. The changes in optical properties are attributed mainly to carrier confinement effects caused by variation of In content contrast between the QR material and the surrounding well.

Optimization and application of on-chip terahertz Goubau lines

2013 38th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2013

ABSTRACT

Electro-optic and electro-absorption characterization of InAs quantum dot waveguides

Optics Express, 2008

Publisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) ... more Publisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) • A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User

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[The expression of EMS1 and DcR3 protein in laryngeal carcinoma and the relation between EMS1 and DcR3]

Lin chuang er bi yan hou tou jing wai ke za zhi = Journal of clinical otorhinolaryngology, head, and neck surgery, 2010

To investigate the expression of EMS1 and DcR3 in laryngeal carcinoma and analyze the relation of... more To investigate the expression of EMS1 and DcR3 in laryngeal carcinoma and analyze the relation of EMS1 and DcR3. The expression of EMS1 and DcR3 protein in 41 laryngeal carcinoma fresh samples and 41 para-carcinoma tissues (to cutting margin > 0.5 cm) were measured by flow cytometry, and 15 normal laryngeal mucosa samples were also studied as controls. (1) The quantitative and qualitative expression of EMS1 and DcR3 protein in laryngeal carcinoma tissues was obviously higher than those in para-carcinoma and in normal laryngeal mucosa tissues respectively (P < 0.05). There was no significant difference between the expression of para-carcinoma and normal laryngeal mucosa tissues. (2) In laryngeal carcinoma, the expression of EMS1 and DcR3 protein was independent of patients' clinical classification, tumor size, smoking history, patients' age and sex but associated with tumor metastasis, pathological grade and clinical stage. (3) In laryngeal carcinoma, the expression of ...

The Influence of Nitrogen Clustering Effect on Optical Transitions in GaInNAs/GaAs Quantum Wells

physica status solidi (c), 2003

... Fig. 1. Temperature-dependent PL spectra of Ga0.89In0.11N0.01As0.99/ GaAs MQW under the excit... more

Polarized photoreflectance and photoluminescence spectroscopy of InGaAs/GaAs quantum rods grown with As2 and As4 sources

Nanoscale Research Letters, 2012

We report photoreflectance (PR) and photoluminescence (PL) investigations of the electronic and p... more We report photoreflectance (PR) and photoluminescence (PL) investigations of the electronic and polarization properties of different aspect ratio (height/diameter) InGaAs quantum rods (QRs) embedded in InGaAs quantum wells (QWs). These nanostructures were grown by molecular beam epitaxy using As 2 or As 4 sources. The impact of the As source on the spectral and polarization features of the QR-and QW-related interband transitions was investigated and explained in terms of the carrier confinement effects caused by variation of composition contrast between the QR material and the surrounding well. Polarized PR and PL measurements reveal that the polarization has a preferential direction along the [ 110] crystal axis with a large optical anisotropy of about 60% in the (001) plane for high aspect ratio (4.1:1) InGaAs QRs. As a result, in PL spectra, the transverse magnetic mode dominated (110)-cleaved surfaces (TM [001] > TE [110] ), whereas the transverse electric mode prevailed for (110)-cleaved surfaces (TM [001] < TE [1 10] ). This strong optical anisotropy in the (001) plane is interpreted in terms of the hole wavefunction orientation along the [ 110] direction for high aspect ratio QRs.

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