Fabrication of eight-step diffractive optical element for hologram-ROM

The research and development of the holographic data storage (HDS) is advanced, as one of the high-speed, mass storage systems of the next generation. Recently, along the development of the write-once system that uses photopolymer media, large capacity ROM type HDS which can replace conventional optical discs becomes important. In this study, we develop the ROM type HDS using a diffractive optical element (DOE), and verify the effectiveness of our approach. In order to design DOE, iterative Fourier transform algorithm was adopted, and DOE is fabricated with electron beam (EB) cutting and nanoimprint lithography. We optimize the phase distribution of the hologram by iterative Fourier transform algorithm known as Gerchberg–Saxton (GS) algorithm with the angular spectrum method. In the fabrication process, the phase distribution of the hologram is implicated as the concavity and convexity structure by the EB cutting and transcribed with nanoimprint lithography. At this time, the mold is formed as multiple-stage concavity and convexity. The purpose of multiple-stage concavity and convexity is to obtain high diffraction efficiency and signal-to-noise ratio (SNR). Fabricated trial model DOE is evaluated by the experiment.

State-of-the-art diffractive optical elements (DOEs) and computer generated holograms (CGHs) are fabricated using e-beam lithography and dry etching techniques to achieve multi-level phase elements with very high diffraction efficiencies. Electron beam lithography allows DOEs/CGHs with smaller feature sizes (e.g. for off-axis diffractive lenses with small f-number) to be fabricated. Dry etching techniques, especially chemically assisted reactive ion beam, allows DOEs/CGHs be fabricated in a variety of materials. Multi-level phase DOEs/CGHs, especially those of sixteen or more phase levels, mean their surface profiles are fabricated with high accuracy / quality. It is not only the e-beam system which dictates the feature size limitations, but also the alignment systems (mask aligner) and the materials (e-beam or photo resists). In order to allow DOEs/CGHs to be used in new optoelectronic systems, it is necessary also to fabricate the elements in different materials economically. Since the cost of a multi-level phase DOE/CGH is determined by the e-beam writing time, the number of etching steps for fabricating the master, and the technology for replication, we need to decrease the writing time and etching steps for the master and to develop a low cost replication technology for mass production without affecting the quality of the DOEs/CGHs. In this Chapter, we will review three DOE/CGH fabrication techniques and CAD development required, considering the overall design and fabrication time for multi-level phase DOEs.

Optical lithography with its 193nm technology is pushed to reach and shift its limits even further. There is strong demand on innovations in illumination part of exposure tools. Current illumination systems consisting of diffractive and refractive optical elements offer numerous benefits such as optimized laser beam shape with high homogeneity and high numerical aperture enabling high efficiency. LIMO's unique production technology is capable to manufacture free form surfaces on monolithic arrays larger than 250mm with high precision and reproducibility. Different kinds of intensity distributions with best uniformities or customized profiles have been achieved by using LIMO's refractive optical elements. Recently LIMO pushed the limits of this lens production technology and was able to manufacture first diffractive optical elements (DOE) based on continuous relief's profile. Beside for the illumination devices in lithography, DOEs find wide use in optical devices for other technological applications, such as optical communications and data processing. Up to now DOE designs follow the principle of phase diffraction gratings. Its diffraction structure with a periodic phase profile performs a superposition of beams with predefined energy ratios. Due to the application for high precise laser-beam shaping and beam splitting in optical technologies and optical fiber networks, number of grating orders is increased up to some tens or even hundreds. Classic lithographic technologies lead to quantized (step-like) profiles of diffractive micro-reliefs, which causes a decrease of beam splitter's diffractive efficiency. The newest development of LIMO's microlens fabrication technology allows us to make a step from free programmable microlens profiles to diffractive optical elements with high efficiency. Our first results of this approach are demonstrated in this paper. Diffractive beam splitters are presented. A special mathematical method is used to design diffractive optical elements with continuous surface profiles. Comparison between theoretical simulations and experimental results shows very good correlation.

Low cost, rapid fabrication of durable molds of grating arrays for nanoimprint lithography

Optical microsensors for fluid flow diagnostics

Summary form only given. Nanoscale metal-semiconductor-metal (MSM) photodetectors and MESFETs are key elements in ultra-fast optical and wireless communication systems. However, devices with sub-0.25 /spl mu/m feature sizes are typically fabricated using electron-beam lithography (EEL), which has high cost and low throughput. Nanoimprint lithography (NIL), on the other hand, has both low cost and high throughput, as well as sub-l0 nm resolution. We report the fabrication of MSM photodetectors on semi-insulating (SI) GaAs using NIL, and the examination of NIL on the quality of the nanoscale Schottky contact. We found that if the imprint pressure is 600 psi or lower, nanoscale GaAs MSM photodetectors fabricated using NIL are comparable to those fabricated by conventional EEL and photolithography, indicating no degradation to the photodetector Schottky contact induced by the imprint process.

Oblique incidence is the normal working mode for diffractive optical elements (DOEs). The diffraction efficiency is very sensitive to the angle of incidence for multilayer diffractive optical elements (MLDOEs). Therefore, the design and diffraction efficiency analysis of MLDOEs with wide angles of incidence is of universal significance and practice. We propose an integral diffraction efficiency model for MLDOEs with wide angles of incidence in case of polychromatic light and then describe this corresponding optimal design in detail. It is shown that high diffraction efficiency can be realized by the surface micro-structure heights optimization, ensuring high modulation transfer function (MTF) for MLDOEs with wide angles of incidence in hybrid optical systems. On this basis, we present the optimal design process and simulation of an MLDOE working in visible waveband with optical plastic materials combination PMMA and POLYCARB as the two-layer substrates. The result shows that with this optimal design, we can achieve the maximum diffraction efficiency and minimum micro-structure heights, which makes the MLDOE design exactly over the entire waveband and wide angles of incidence especially for zoom hybrid optical system.

Shaping of laser light intensities by using Diffractive Optical Elements allows the adaption of the incident light to its application. Fused silica is used where for example UV-light or high temperatures are mandatory. For high diffraction efficiency the quality of the etched surface areas is important. The investigation of different process parameters for Ion Beam and Reactive Ion Etching reveals that only Ion Beam Etching provides surfaces with optical quality. Measurements of the influence of the surface quality on the diffraction efficiencies prove that the surfaces generated by Reactive Ion Etching are not suitable. Due to the high selectivity of the process Reactive Ion Etching is nevertheless a reasonable choice for the fabrication of Diffractive Optical Elements. To improve the quality of the etched surfaces a post processing with Ion Beam Etching is developed. Simulations in MATLAB display that the angle dependent removal of the surface during the Ion Beam Etching causes a smoothing of the surface roughness. The positive influence of a post processing on the diffraction efficiency is outlined by measurements. The ion beam post processing leads to an increase of the etching depth. For the fabrication of high efficient Diffractive Optical Elements this has to be taken into account. The relation is investigated and transferred to the fabrication of four-level gratings. Diffraction efficiencies up to 78 % instead of the ideal 81 % underline the practicability of the developed post processing.

This paper is dedicated to the development of synthesis methods for diffractive optical elements (DOEs) on non-planar surfaces. To form 3D images, a set of color 2D frames is used, visible to an observer from different observation points. The developed DOEs can be called a stereogram with a 360-deg view when the DOE is illuminated with white light. Methods are developed for computing the phase function of the DOE and are applicable to a wide range of convex surfaces. However, the manufacturing technology used limits this range to conical and cylindrical surfaces. The microrelief of the flat DOE is produced using electron-beam lithography. A video recorded using optical elements produced demonstrates the capabilities of the technologies developed. These DOEs can be used to protect brands against counterfeit.

The descriptions of the new products listed in this section are based on information supplied to us by the manufacturers. Physics Today can assume no responsibility for their accuracy. For more information about a particular product, visit the website at the end of the product description. Magnetic force microscopy probesSection:ChooseTop of pageMagnetic force microscopy... <<Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESNANOSENSORS has introduced a new series of six silicon probes for magnetic force microscopy that make possible the visualization of magnetic domains. The probes are optimized for high sensitivity and enable tapping mode and noncontact and lift modes in air. The standard MFM probes feature a hard magnetic coating for high magnetic contrast and high lateral resolution. The low-momentum probes are designed for reduced disturbance of the magnetic sample by the tip and for enhanced lateral resolution. Low-coercivity MFM probes are coated with a soft magnetic thin film to allow the measurement of domains in soft magnetic samples. For high-resolution magnetic imaging, NANOSENSORS offers the SuperSharp-Silicon tip. Two types of probes have been developed for use in ultrahigh vacuum. NANOSENSORS, Rue Jaquet-Droz 1, CP 216, CH-2002 Neuchatel, Switzerland, http://www.nanosensors.com See www.pt.ims.ca/12307-131 Silver nanoparticles Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticles <<Atomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESAmerican Elements has announced expansion of the manufacture of silver oxalate, a precursor for the production of silver nanoparticles. The nanoparticles, nanodots, and nanopowder can be either spherical high-surface-area metal particles, typically 10-, 40-, and 80-nm o.d., with specific surface area in the 30–60 range m2/g, or flakes with an average particle size of 2–10 µm, with an SSA of approximately 40–80 m2/g. The silver particles are available in high purity and ultrahigh purity and in coated and dispersed forms. Applications for the product include as an antimicrobial, antibacterial, antiviral, antibiotic, and antifungal agent when incorporated in coatings, nanofibers, plastics, soap, textiles, and self-cleaning fabrics. It is also used in nanowire and certain catalyst applications. American Elements, 1093 Broxton Avenue, Suite 2000, Los Angeles, CA 90024, http://www.americanelements.com See www.pt.ims.ca/12307-132 Atomic force microscope Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscope <<Scanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESPacific Nanotechnology has developed the Nano-DST, a complete atomic force microscope (AFM) system that includes advanced control software, a high-performance electronic controller, a versatile stage, and a vibration solution. A dual scanner control enables two scanners to be driven individually or simultaneously to perform rapid scanning and panning. With the company’s flexure scanner, which uses 3D calibration sensors, optional scan ranges as high as 350 µm are possible; 24-bit scan control and 400-MHz high-stability modulation electronics are included. The Nano-DST stage is constructed with a precision granite base and a gantry that supports a video optical microscope, light lever AFM scanner, and the high-speed sample rapid scanner. The stage features seven stepper motors that control the sample position, optics zoom, and focus. Pacific Nanotechnology Inc, 3350 Scott Boulevard, Suite 29, Santa Clara, CA 95054, http://www.pacificnano.com See http://www.pt.ims.ca/12307-133 Scanner for nanotechnology Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog... <<Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESPhysik Instrumente is offering the P-363 PicoCube XY/XYZ, a high-performance, closed-loop piezo scanning system designed for atomic force, scanning probe, and scanning tunneling microscopy. It combines the ultralow-inertia, high-speed piezo scanner with noncontact, direct-measuring, parallel metrology capacitive position sensors capable of 50-pm resolution. The sensors measure the actual distance between the fixed frame and the moving part of the stage, which results in a stiffer, faster-responding servo-loop. The very fast xyz piezo drives offer resonant frequencies of 9.8 kHz in z and greater than 3 kHz in x and y. The high frequency and high-bandwidth capacitive feedback allow step and settle to 1% accuracy in as little as 1 ms. The company can now provide the E-536 driver/controller for use with the PicoCube. Physik Instrumente LP, 16 Albert Street, Auburn, MA 01501, http://www.pi-usa.us See www.pt.ims.ca/12307-134 Nanoimprint lithography Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithography <<Digital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESMolecular Imprints has introduced the Imprio 1100 system, which provides fully automated nanoimprint lithography. The system combines the resolution and CD control of e-beam lithography with the throughput, overlay, and operating simplicity of a mask aligner, and it can be configured to accept 25- to 150-nm substrates. The Imprio 1100 delivers cost-effective patterning of sub-50 nm features on the fragile, nonflat substrates used in the compound semiconductor industry. The same processes can also be used to pattern larger features such as laser diode ridges and diffractive optical elements with high pattern fidelity. The system is ideally suited for application in LEDs, optical components requiring fine-resolution patterning and 3D features, and high-density disk substrates for hard disk drives. Molecular Imprints Inc, 1807 West Braker Lane, Building C-100, Austin, TX 78758-3605, http://www.molecularimprints.com See www.pt.ims.ca/12307-135 Digital microscopeSection:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscope <<X-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESThe KH-7700 digital microscope from Hirox Inc combines as one unit a digital camera, light source, integrated LCD monitor, computer, and software. The camera incorporates a CCD image sensor with approximately 2.11 million pixels and provides a rate of 15 frames/s. It offers a still image capture of up to 30 million pixels and dynamic image recording with selectable resolution. The light source is a 60-W short-arc metal halide lamp with an average life of 4000 hours. A modular lens system with 1× to 7000× magnification is optimized for the CCD sensor and offers viewing from straight and oblique angles. For 2D and 3D measurements of height and volume, an autocalibration select feature enables users to zoom in and out while the scale and calibration in the unit changes accordingly. The KH-7700 has 3D image rendering software with profiling that uses split images and image comparison. Hirox-USA Inc, 1060 Main Street, Suite 302, River Edge, NJ 07661, http://www.hirox-usa.com See www.pt.ims.ca/12307-136 X-ray source for structural biologySection:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur... <<Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESRigaku Americas Corp has announced the FR-E+ SuperBright, an ultrabright, microfocus rotating anode x-ray source for structural biology. With an intensity up to 1.6 ×1011 x-rays/mm2/s, the brightness of the new source exceeds some second-generation synchrotron beamlines; the company claims that the new device is the most intense home laboratory x-ray source now available for macromolecular crystallography. The FR-E+ SuperBright features a true 70 µm × 70 µm focal spot, reportedly the smallest available in a rotating anode design. The beam is ideally suited to the tiny crystals typically encountered in current structural biology research. The new system can be supplied in several dual-wavelength configurations, including one using copper and chromium. Rigaku Americas Corporation, 9009 New Trails Drive, The Woodlands, TX 77381-5209, http://www.rigaku.com See www.pt.ims.ca/12307-137 Spectroscopic ellipsometer Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete... <<Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLES Ocean Optics’ SpecEl-2000-VIS is a benchtop spectroscopic ellipsometer that uses polarized light reflected from the surface of a substrate to measure thin films. It provides fast, precise determination of layer thickness, refractive index, absorption, and components ratio and is well suited for semitransparent flat samples such as wafers and glass plates. Compared with reflectometry, spectroscopic ellipsometry measures relative changes in the phase and amplitude of the light instead of absolute intensity. Depending on the layer and substrate material, the SpecEl can detect over the full 450- to 900-nm spectral range layer thicknesses between 1 nm and 5 µm and refractive indices to ±0.005°. The software enables experiment methods to be configured and saved for one-step analysis. Ocean Optics Inc, 830 Douglas Avenue, Dunedin, FL 34698, http://www.oceanoptics.com See www.pt.ims.ca/12307-138 Wafer loader for microscopy Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco... <<Camera for biofluorescenc...Microfluidic componentsNew literatureCITING ARTICLESMcBain Instruments is offering a newly designed laboratory tool, the Wafer Handler WL150 and WL200 series of semiautomatic wafer inspection systems. The portable apparatus offers high throughput at 750 wafers/h with smooth handling of wafer sizes up to 8 in.; the company’s new wafer cassettes accommodate either 3–6 in. (WL150) or 5–8 in. (WL200) sizes. The class 1 clean-room-compatible wafer handler features smart stepper motors for the drive axis motors that provide stall and fault detection, linear stages for smooth and repeatable action, and vacuum touch end effectors with sensing capabilities. The device facilitates safer wafer handling with a spring-loaded counterbalance to support the weight without overloading the z-axis mechanism. McBain Instruments, 9601 Variel Avenue, Chatsworth, CA 91311, http://www.mcbaininstruments.com See www.pt.ims.ca/12307-139 Camera for biofluorescence microscopy Section:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc... <<Microfluidic componentsNew literatureCITING ARTICLESPhotron has developed the FocusScope SV200-i, a new slow-motion video system for the study of extreme low-light biofluorescence and microscope recording at rates up to 2000 frames/s. Other applications include high-speed imaging of blood cells and quantum-dot response measurements. The camera’s image intensifier (a luminous gain of 2.2 × 104 lm/m2/lx) is bonded directly to the CMOS sensor and provides 512 × 512 pixel resolution. The gallium arsenide phosphide photocathode delivers a broad spectral response over the 280–720 nm spectral range with a peak sensitivity at 530 nm. Intensifier overbrightness protection is enabled through phosphor-surface current detection. Additional features of the FocusScope SV200-i are low-light-level framing and gray-scale enhancement. Photron USA Inc, 9520 Padgett Street, Suite 110, San Diego, CA 92126-4446, http://www.photron.com See www.pt.ims.ca/12307-140 Microfluidic componentsSection:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic components <<New literatureCITING ARTICLESLabSmith has introduced its CapTite microfluidic series of components for fast assembly of microfluidic setups. The components, licensed from Sandia National Laboratories, are designed for construction using 360-µm capillary tubing and include breadboards, valves, tees and ferrules, refillable microliter volume cartridges, Luer-Lock connectors to interface with standard syringe pumps, and bonded-port connectors to route fluids through and between microfluidic chips. The compact components are designed for leak-free connectivity, even at high pressures, and for low dead volumes and easy cleaning. Complete microfluidic construction kits are available; users can choose from single user, capillary interface, and chip interface types. LabSmith Inc, 7665 Hawthorne Avenue, Livermore, CA 94550, http://www.labsmith.com See www.pt.ims.ca/12307-141 New literatureSection:ChooseTop of pageMagnetic force microscopy...Silver nanoparticlesAtomic force microscopeScanner for nanotechnolog...Nanoimprint lithographyDigital microscopeX-ray source for structur...Spectroscopic ellipsomete...Wafer loader for microsco...Camera for biofluorescenc...Microfluidic componentsNew literature <<CITING ARTICLESInnoCal, an accredited metrology laboratory, has issued a service brochure that provides a comprehensive explanation of its many traceable calibration and repair services for a wide range of instrumentation. InnoCal, 625 East Bunker Court, M/S 14, Vernon Hills, IL 60061-1844, http://www.innocalsolutions.com ▪ See www.pt.ims.ca/12307-142 © 2007 American Institute of Physics.

Diffraction efficiency model for diffractive optical element with antireflection coatings at different incident angles

Diffractive optical elements (DOEs) of the kinoform type have been fabricated on DuPont photopolymer by using a gray scale mask technology. The fabricated DOEs have high diffraction efficiency and low noise. Compared with the conventional DOE fabrication the new process is rather simple and does not involve expensive capital equipment such as mask aligners and dry etching systems, and can be extended to mass production.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Nanophotonics is wide field covering many interesting applications branching from cutting edge science including plasmonics, metamaterials, cavity quantum electrodynamics in high-Q cavities all the way to applied sciences like silicon nanophotonics for on chip optical interconnections and single frequency semiconductor light sources. Most of the practical device demonstrations in these fields utilize nanopatterned surfaces. Applications require patterning of nanoscopic gratings, photonic crystals, waveguides and metal structures. There are many wonderful demonstrations of nanotechnology-based lasers and other photonic components. However, difficult questions related to fabrication need to be addressed before these components enter any market. Demonstrations in the scientific literature have relied heavily on the use of direct writing lithography methods, such as electron beam lithography or focused ion beam lithography. These methods, although excellent for scientific studies, cannot be scaled up to allow cost effective production of nanophotonics. Lithography solutions developed for integrated circuits can produce extremely narrow linewidths and deliver high precision but are difficult to transfer to photonics fabrication. There exist many alternative lithography methods, but their scale-up to cost effective volume production is challenging. Since the introduction of nanoimprint lithography (NIL) in 1995 (Chou et al. 1995), there has been widespread interest in the development of NIL for various applications. As early as in 2003 NIL had gained substantial support and was chosen as one of MIT's Technology Review’s “10 Emerging Technologies That Will Change the World” (Technology Review 2003). The selection was justified by the fact that NIL can bridge the gap between lab level nanotechnology research and production level manufacturing requirements. In this chapter, we briefly review the state-of-the-art lithography methods and introduce nanoimprint lithography (NIL), a very cost effective lithography method for nanophotonics applications. In section two we will introduce soft UV-NIL, an imprint method using soft and flexible stamps, as a method for patterning compound semiconductor optoelectronics. Finally, in section three, we highlight some NIL activities based on soft-UV-NIL.

The progress in optics is related to wide application of computer-synthesized diffractive optical elements (DOE). The lithography technology allows one to fabricate easily a DOE with binary profile. Using a set of N = 3-4 masks one can fabricate multilevel DOE with the diffraction efficiency (DE) over 90% [1]. Another way to form a DOE profile is based on incoherent spatial filtering of a periodic mask spectrum and bleaching of the exposed film [2]. This method simplifies substantially the process of DOE fabrication because it does not involve fabrication and aligning of a set of masks. However, this method allows to fabricate only periodic DOE.

The recent growth of information-communication facilities such as the Internet, mobile telecommunication and video-on-demand services has led to explosion of worldwide communication traffic, which increase demand for faster and denser communication infrastructures including optical communication networks. Distributed feedback laser diodes (DFB LDs) have been widely used as optical sources in networks because of their high selectivity and stability of wavelength. Although they had limitedly been used in longhaul and high-speed network at one time, they are now increasingly required in metro and end-user fields because of the increasing traffic. Thus, necessity for inexpensive DFB LDs increases rapidly. The characteristics of a DFB LD with uniform (constant period) gratings depend on the grating phase at the cleaved facet (Matsuoka et al., 1984). The variation of characteristics with the facet phase is a serious issue in view of productivity and usability of the LDs. One of the most effective ways of reducing the facet phase effect is to adopt phase-shifted gratings instead of uniform gratings (Kaden et al., 1992). The uniformities of the LD characteristics such as mode-stability and output power are improved by adopting phaseshifted gratings, thus the yield of LDs increase and their production cost is effectively reduced. In general, there are various fabrication methods for diffraction gratings of DFB LDs, for example, interference exposure, electron beam lithography (EBL), and optical projection exposure. Interference exposure cannot feasibly be used for fabricating phase-shifted gratings, because it exclusively generates exposure patterns with a uniform bright-and-dark period. Although EBL has sufficient resolution to be used for phase-shifted gratings, exceedingly expensive apparatus is necessary for volume production with sufficient throughput. For the optical projection method, a forefront stepper having sufficient resolution for gratings is also expensive, and the cost is too high for fabricating DFB LDs, of which production volume is relatively small compared to that of such semiconductor devices as LSIs. Nanoimprint lithography (NIL) has been studied by many organizations since the middle of the 1990s. Chou et al. indicated that sub-10-nm features could be formed by imprint, which started the era of NIL technology (Chou et al., 1995). A novel method of NIL using a UVcurable resin was introduced by Haisma et al (Haisma et al., 1996), and Bailey et al.