Embedded nano channels fabricated by non-selective reverse contact UV nanoimprint lithography technique

In this work, a novel nanofabrication technique is presented, namely “Reverse contact Ultraviolet Nanoimprint Lithography” (RUVNIL). It is based on reverse nanoimprint lithography and ultraviolet contact lithography. It provides flexibility in building complex three-dimensional structures allowing selective imprint over pre-patterned surfaces with or without residual layer in opposition to what is often encountered in the normal NIL process. We have investigated and optimized the imprinting parameters that are required for three-dimensional nanofabrication and applied it to the fabrication of nano-fluidic channels. This lithography technique is a very promising process for three-dimensional nanofabrication.     

采用IFVD-QWI技术制备电吸收调制DFB激光器

采用等离子体增强化学气相沉积 (PECVD) 法在I nGaAsP多量子阱/InP缓冲层/InGaAs层上沉积SiO₂薄膜,通过N₂气氛下快速热退火(RTA )方法实现无杂质空位扩散(IFVD)的量子阱混杂(QWI)。对不同退火温度下量子 阱增益峰值波长的蓝移特性进行了实验摸索,在780℃@80s的退火条 件下,可以获得最大72.8nm的相对波长 蓝移量,并且发现快速热退火RTA温度低于780℃以下时,LD区的波长 蓝移量随温 度变化基本能控制在10nm以内。 通过选取合适退火条件实现了光荧光(PL)峰值波长约50nm的蓝移量, 在选区制备出合适带隙波长材料的基 础上,在LD区制作全息光栅并二次外延P型掺杂电接触层后,采用标准化浅脊波导电吸收 调制(EAM)分布反馈 激光器(EML)工艺制备了1.5μm波长的EML管芯,器件阈值为 20m A,出光功率达到2mW@90mA,静态消光比在＋6V反偏压下为9.5dB。     

用深紫外光刻波带片制作全息透镜阵列和椭圆波带片

本文报道用电子束扫描和深紫外曝光获得的离子刻蚀波带片的一级衍射波和二级衍射波干涉,分别在银盐干板和光致抗蚀剂上制作平面全息透镜阵列和椭圆波带片,并给出用它们聚焦和成像的实验结果。     

High-quality InP surface corrugations for 1.55 ?m InGaAsP DFB lasers fabricated using electron-beam lithography

Second-order surface corrugations for 1.55 ?m distributed feedback (DFB) lasers have been fabricated in InP with a high yield using electron beam exposed resist masks. Attractive features of this technique are its flexibility and variable mark/space ratio (for optimum DFB coupling strength). Diffraction experiments show these gratings to be of suitably high optical quality.     

Fabrication of second-order gratings for 1.55 μm DFB lasersusing deep UV lithography

Second-order gratings for 1.55 μm DFB lasers have been fabricated on InP substrate using contact deep UV (220 nm) lithography. Localised gratings with a 0.48 μm pitch were clearly resolved in PMMA photoresist and then transferred in InP by wet chemical etching     

Low-threshold 1.5 mu m DFB laser grown by GSMBE

GaInAsP 1.5 mu m DFB lasers with a low threshold current (17 mA) have been grown by gas source molecular beam epitaxy (GSMBE) in a two-step epitaxial process. The lasers exhibit single-mode emission for emitted power in excess of 10 mW with side mode suppression ratio of 40 dB and spectral linewidth of 15 MHz. In addition the dispersion of the lasing wavelength has been found to be as low as 1.7 nm.<>     

DFB LD manufactured by nanoimprint lithography

Gratings of distributed feedback laser diodes (DFB LDs) have been successfully manufactured by nanoimprint lithography (NIL). Uniform gratings with periods of about 240 nm and phase-shifted in the center have been fabricated by a soft press NIL employing a polymer stamp technology. Moreover, the shape of the grating is rectangle, rather than sinusoidal by holography.The test results show good characteristics of the electrical and spectral output. The results of this study indicate that NIL has high potential for the manufacture of DFB LDs.     

Azide-phenolic resin photoresists for deep UV lithography

A photosensitive composition, consisting of an aromatic azide compound (3,3'-diazidodiphenyl sulfone) and a phenolic resin (poly(p-vinylphenol)), called MRS-1, has been prepared and evaluated as a negative deep UV resist for high resolution lithography. Solubility of MRS-1 in an aqueous alkaline developer decreases upon exposure to deep UV radiation. The alkaline developer removes the unexposed areas of MRS-1 by an etching-type development process. No swelling-induced pattern deformation occurs, and images of submicrometer resolution are obtained. The resist is approximately two orders of magnitude more sensitive than PMMA(polymethyl methacrylate). The exposure time of 5 s is sufficient for deep UV contact printing using a 500-W Xe-Hg lamp. The resistance to dry etching of MRS-1 is comparable to that of conventional positive photoresists based on phenolic resin.     

Gold nanohole arrays for biochemical sensing fabricated by soft UV nanoimprint lithography

We report on results of fabrication and optical characterisation of sub-250 nm periodic gold nanohole arrays on glass by using UV nanoimprint lithography (UV-NIL) combined with both reactive ion etching (RIE) and Cr/Au lift-off processes. The transmission spectra of the fabricated nanohole gratings were measured for different hole diameters and periods. We also show preliminary results of chemical sensing after surface modification of the gold hole arrays. In agreement with the theoretical prediction, we found that any change in the dielectric index of the surrounding environment of the metallic array produces a transmission peak red shift.     

Investigation on the spectral characteristics of DFB lasers withdifferent grating configurations made by electron-beam lithography

The single-mode stability for distributed-feedback (DFB) lasers with various electron-beam-written grating configurations has been investigated theoretically and experimentally, for both as-cleaved and AR-coated lasers. Other laser properties interesting for coherent and multichannel communications systems, such as linewidth and tunability, have also briefly been investigated. Lasers with more sophisticated grating structures, such as an optimized multiple phase-shifted or a corrugation-pitch-modulated grating, did not exhibit performance significantly superior to that of λ/4-shifted DFB lasers with an appropriate coupling coefficient. Antireflection (AR)-coating of the end facets proved indispensable for obtaining a high yield for lasers with single-mode operation at high output power and for reducing the large chip-to-chip variation seen for the as-cleaved lasers. A theoretical investigation of the effect of end reflections on the stopband and of the problem of determining the coupling coefficient was also made     

Integratable, high speed buried ridge DFB lasers fabricated on semi-insulating substrates

The fabrication of buried ridge DFB lasers on semi-insulating substrates is described. A novel contacting mechanism was employed to give a series resistance of less than 4 Omega . Devices were fabricated at both 1.3 and 1.53 mu m with lasing thresholds as low as 16 mA. Single longitudinal mode operation was achieved with SMSR greater than 30 dB at both wavelengths. The structure gives an inherently low capacitance, which together with low threshold currents, low series resistance and fabrication on SI substrates makes these devices suitable for integration and high speed applications.<>     

Ultrafast deep UV Lithography with excimer lasers

The use of high-power pulsed excimer lasers for photolithography is described for the first time. Short exposure times, high resolution and absence of speckle are experimentally demonstrated. Using a XeCl laser at 308 nm and a KrF laser at 248 nm, excellent quality images are obtained by contact printing in two positive photoresists. Resolution down to 1000 line-pairs/mm is demonstrated. These images are comparable to state-of-the-art lithography done with conventional lamps; the major difference is that the excimer laser technique is ∼ 2 orders of magnitude faster. Preliminary results on reciprocity behavior in several resists are also presented.     

Multi-quantum-well lasers emitting at 1.55 mu m grown by GSMBE

GaInAs/GaInAsP multi-quantum-well structures emitting at 1.55 mu m have been realised by gas source molecular beam epitaxy (GSMBE) over a large range of growth temperature. Threshold current densities as low as 0.81 kA/cm/sup 2/ have been obtained. The first BH lasers fabricated by GSMBE from these heterostructures exhibit low threshold current (18 mA) and linear DC light-current characteristics up to 20 mW.<>     

Microlenses fabricated by discontinuous dewetting and soft lithography

This letter describes an approach to fabricating microlens arrays with low cost and large area through the combination of discontinuous dewetting and reversible water-ice transition via a soft lithography replica process. Microlenses with different curvature can be tuned by the modulation of the wettability of the substrates. The microlenses fabricated can project clear miniaturized images.     

High performance DFB-MQW lasers at 1.5 mu m grown by GSMBE

1.5 mu m GaInAs multiquantum well distributed feedback lasers have been successfully fabricated on an InP grating substrate by GSMBE. DFB mode oscillation at high output power (50 mW) and narrow linewidth (1.3 MHz) have been obtained.<>     

Room-temperature operation of patterned quantum-dot lasers fabricated by electron beam lithography and selective area metal-organic chemical vapor deposition

We have developed a quantum-dot fabrication process which allows for explicit definition of the location and lateral dimension of quantum dots using electron beam lithography and selective area metal-organic chemical vapor deposition. We have demonstrated the first reported room-temperature operation of a patterned quantum-dot edge-emitting laser based on this fabrication technique.     

1.53 ?m DFB lasers by mass transport

DFB lasers emitting at ?=1.53 ?m made by mass transport have been demonstrated. Output power exceeding 5 mW/ facet was obtained when operated in CW at room temperature. Single-longitudinal-mode operation with a minimum threshold current of 26 mA was achieved. No degradation can be observed after aging at 5 mW continuous power at room temperature for more than 1000 h.     

GaAs field effect transistors fabricated by imprint lithography

A GaAs metal–semiconductor field-effect transistor (MESFET) has been realized based on mix-and-match fabrication using optical lithography for the ohmic contacts and imprint lithography for the gate. The gate length and width are 1.2 and 80 μm, respectively, the channel length is 4 μm. For the gate definition a Si-mold is embossed into a thin polymer film located on top of an n-doped GaAs layer. The gate is fabricated by metal evaporation and lift-off.     

Optically variable micro-mirror arrays fabricated by graytone lithography

The fabrication of micro-mirror based portrait and non-portrait images has been demonstrated by graytone lithography. The depiction of a portrait image was achieved by a novel modulation of the width of micro-apertures in the variable transparency mask. The non-portrait image was encoded as micro-mirrors of an opposing slope and orientation. An optical switch effect between the portrait and a non-portrait image was encoded into the mask by the arrangement of the micro-mirrors as a separate interleaved channel for each image. The lithographic exposure of the pattern into a layer of thick resist has produced an array of micro-mirrors with a depth of 10-30 μm. Various configurations of the micro-mirror arrays have been examined in relation to the type of micro-apertures and their orientation. Optically variable effects achieved in the micro-mirror devices have included a portrait to non-portrait switch, a positive to negative image switch and a non-portrait to non-portrait image switch. The micro-mirror structures have been hot embossed into polypropylene sheet using a Ni shim to create high quality optically variable images.     

Arrays of metallic nanocones fabricated by UV-nanoimprint lithography

We introduce a novel method for fabricating nanocones of various metals. Based on a combination of UV-nanoimprint lithography and electron beam evaporation, the method enables fast, high volume, and reproducible fabrication of conical nanostructures on flat substrates. We investigate cone formation with eight different metals and find that the shape of the cone depends on the material characteristics of the deposited metal.