This paper reports the infrared spectral responses of 17 and 35 μm uncooled bolometers fabricated at INO. They are measured by making use of an external readout circuit along with a monochromator. As expected, the spectral absorption strongly depends on the bolometer stack as well as the pixel layout. By proper selection of design parameters, the spectral response can be made flat from 3 to 14 μm without significant deterioration of the detector figure of merit.
In the MEMS manufacturing world, the "fabless" model is getting increasing importance in recent years as a way for
MEMS manufactures and startups to minimize equipment costs and initial capital investment. In order for this model to
be successful, the fabless company needs to work closely with a MEMS foundry service provider. Due to the lack of
standardization in MEMS processes, as opposed to CMOS microfabrication, the experience in MEMS development
processes and the flexibility of the MEMS foundry are of vital importance.
A multidisciplinary team together with a complete microfabrication toolset allows INO to offer unique MEMS foundry
services to fabless companies looking for low to mid-volume production. Companies that benefit from their own
microfabrication facilities can also be interested in INO's assistance in conducting their research and development work
during periods where production runs keep their whole staff busy. Services include design, prototyping, fabrication,
packaging, and testing of various MEMS and MOEMS devices on wafers fully compatible with CMOS integration.
Wafer diameters ranging typically from 1 inch to 6 inches can be accepted while 8-inch wafers can be processed in some
instances. Standard microfabrication techniques such as metal, dielectric, and semiconductor film deposition and
etching as well as photolithographic pattern transfer are available. A stepper permits reduction of the critical dimension
to around 0.4 μm. Metals deposited by vacuum deposition methods include Au, Ag, Al, Al alloys, Ti, Cr, Cu, Mo,
MoCr, Ni, Pt, and V with thickness varying from 5 nm to 2 μm. Electroplating of several materials including Ni, Au and
In is also available. In addition, INO has developed and built a gold black deposition facility to answer customer's needs
for broadband microbolometric detectors. The gold black deposited presents specular reflectance of less than 10% in the
wavelength range from 0.2 μm to 100 μm with thickness ranging from 20 to 35 μm and a density of 0.3% the bulk
density of gold. Two Balzers thin-film deposition instruments (BAP-800 and BAK-760) permit INO to offer optical thin
film manufacturing. Recent work in this field includes the design and development of a custom filter for the James
Webb Space Telescope (JWST) as collaboration with the Canadian company ComDEV. An overview of the different
microfabrication foundry services offered by INO will be presented together with the most recent achievements in the
field of MEMS/MOEMS.
Previous publications for the JWST-FGS-TFI instrument described the design and fabrication of mirror coatings for
scanning Fabry-Perot etalons. Since that time, we have extended the fabrication process using ellipsometry analysis over
the full operational bandwidth from 1.0 to 5.0 microns for both mirror and anti-reflection coatings. This paper will
present single and multiple layer ellipsometry analysis of the a-Si/SiO<sub>2</sub> optical properties. Analysis improvement came
from a-Si/SiO<sub>2</sub> interface consideration and simultaneous use of ellipsometric data from Woollam V-VASE and IRVASE
instruments. Simulations of reflectance and transmittance based on the ellipsometric analysis results will also be
compared to spectrophotometric measurements for witness pieces.
Earlier publications described a novel approach to the design of mirror coatings for scanning Fabry Perot etalons,. Since that time, we have extended the design process, fabricated mirror coatings and used them to build etalons.
One design process improvement is the minimization of off-axis de-tuning. It can be significantly worse with a real mirror coating than the normal "blue shift" associated with the basic Fabry-Perot geometry. This option provides for the control of de-tuning in optimization. Another improvement is optimization for multiple-order operation of the etalon. This technique reduces etalon mirror travel while allowing tunability over a broad spectral range.
The focus of this paper, however, is the experimental results obtained for coatings and etalons built for the Fine Guidance Sensor-Tunable Filter Imager (FGS-TFI) - a Canadian Space Agency funded science instrument for the James Web Space Telescope (JWST). We present measured data for both the coating and the etalon performance.
The Canadian contribution to the James Webb Space Telescope (JWST) mission will be the Fine Guidance Sensor (FGS), incorporating a science-observing mode using tunable filters. We describe here the requirements, the opto-mechanical design concept and bread-board test results for the JWST FGS tunable filters. The FGS requires two continuously tunable filters over the wavelength ranges 1.2 - 2.4 microns and 2.4 - 4.8 microns each having a spectral resolution in the range of R~70 to 200. The selected implementation uses dielectric coated Fabry-Perot etalon plates with a small air gaps. The design finesse is ~30 and the filters are used in 3rd order. The operating temperature is ~35K. Current coating designs provide implementations that require only five blocking filters in each wavelength range to suppress unwanted orders. The filters will be scanned via the use of low voltage piezo-electric transducers. We present results from cryogenic tests of coating samples, PZT actuators and a structural model. The PZT actuators were found have a displacement of ~3.3 microns at 30K with an applied voltage of 125V, more than sufficient for the required scan of the Fabry-Perot plate spacing. The prototype etalon coating was found to be very stable cryogenically, having a measured change of transmission of only ~1% at 77K. The same coating on a 12.7 mm thick substrate, similar to that planned for the filter, was found to have a 18 nm peak-to-valley surface figure change when cooled to 30K. These results demonstrate that the development of tunable filters for the JWST FGS is on track to meet the technology readiness requirements of the program.
The reflective coatings applied to telescope mirrors affect not only the optical performance, but also affect significantly the telescope operation. Replacement of a primary segment of a large segmented mirror is expected to be a major event. An increased service life span of such segment is of enormous value. The optics community is currently aggressively pursuing development in broadband high reflective durable coatings. We are undertaking research with the goal of a high, broadband reflective coatings that, with appropriate cleaning and in situ maintenance, will provide a service life time of more than seven years. Based on the VLOT (Very Large Optical Telescope) project requirements, we conducted a literature search on available materials, thin film deposition and cleaning processes to get as much information as possible. The results of this survey will be presented as the starting point of our study. Different thin film processes have been identified but energetic processes such as Reactive Low Voltage Ion Plating (RLVIP), Magnetron Sputtering and Ion Beam Assisted Deposition (IBAD) will be of great interest for durable coating fabrication. Regarding the cleaning process, we have concentrated our effort on laser cleaning processes.
This paper reports on the development of dielectric and amorphous silicon-based thin film stacks for applications at room and liquid nitrogen (LN) cryogenic temperatures. The deposition process was performed using assisted energetic evaporation processes such as Reactive Low Voltage Ion Plating (RLVIP) and Ion Assisted Deposition (IAD). Dielectric coatings produced by RLVIP exhibited fairly good stability at LN temperature. Indeed, as compared to room
temperature, a spectral shift of ∇λ0.5 = -2.9 nm at half maximum was obtained for a 3-cavity bandpass filter centered at 1570 nm. Amorphous silicon and silicon dioxide stacks deposited by IAD processes were tested for optical applications. Amorphous silicon thin films showed good mechanical stability at LN temperature. The influence of deposition parameters and operating temperature on the electrical, mechanical and optical properties of amorphous Si
films was investigated.
In this paper, we present the final design of the optical train of WIRCAM, a wide-field infrared camera to be installed in early 2004 at the prime focus of CFHT. This cryogenic camera, optimized for J, H and K operating region, used a 4k x 4k IR detector mosaic fed by a single optical train. The sky will be imaged onto the focal plane at an optical speed of F/3.5 yielding an image scale of 0.3 arcsecond per 18 μm pixel. The design image quality is 0.30 arcsecond 50% diffraction encircled energy over the central 20 arcmin field and no images worse than 0.35 arcsecond over the 29.7 arcminute diameter camera field. The optical design distortion at the corners is less than 1%. The WIRCAM camera have a lyot stop at the telescope image pupil in order to mask background radiation coming from external structures. The image of the pupil is sufficiently sharp for background elimination and impose not more than 2% loss of light from the sky in the K spectral band. We also present an optimization of AR coating for IR based camera weighted by MK atmospheric transmission. We discuss the impact of this coating design method on various camera throughput. We include an efficient technique for ghost analysis based on the detector image. We demonstrate that our design meets the performance requirements from an optical and practical point of view.
In this paper, a detailed study of replication of microlenses by UV-assisted moulding in hybrid glass materials is presented. Circular aspherical, spherical and cylindrical microlenses were designed and fabricated in photoresist by using the grey-scale lithography based on high-energy beam sensitive glass. A semi-transparent replication master was then generated. Hybrid organic-inorganic resins were synthesized by sol-gel processing of functionalized alkoxysilanes. The resin viscosity and refractive index depended on synthesis conditions. Transparent, well adhering, several tens of microns-thick films were deposited on fused silica substrates by adjusting the solvent content of the formulation. The thermal expansion coefficient of our material, determined by a Michelson interferometric technique was 1.75 10<sup>-4</sup> K<sup>-1</sup>. High replication fidelity e. g. better than 5% is demonstrated by controlling changes, at the various process steps, in the radius of curvature i.e. focal lengths of microlenses performing the measurements with a Twyman-Green interferometer. Close to diffraction limited microlenses with f-numbers ranging from f/1.4 to f/10 were fabricated.
A numerical propagation algorithm is presented that applies to a particular class of partially coherent beams. The algorithm
relies on the azimutal decomposition of the cross-spectral density (or mutual intensity) of the field, which reduces the usual
four-dimensional propagation integral into a series of two-dimensional integrals that can be treated using fast Hankel
Numerical simulations and experiments indicate that a graded reflectivity minor can improve the fundamental mode
performance of moderate gain lasers operated with a stable resonator. Sizeable increases in TEM output power and far-field
radiance are achievable.
The graded reflectivity mirror (GRM) unstable resonator has become the resonator of choice for many laser systems. It provides a large size fundamental mode while reducing detrimental diffraction effects encountered in hard-edge unstable resonators. It also allows some control over the near-field profile of the output beam through a proper choice of the reflectivity profile of the GRM. This added flexibility in design translates into an apparent increase in complexity to the potential user. This tutorial review discusses through a step-by-step approach the inner workings of such resonators, in order to identify tradeoffs which are involved in their design. Geometrical and diffractive contributions to the mode definitions are discussed, as well as the beam shaping action of amplification. Particular attention is given to super-Gaussian resonators, which are nowadays the most widely used.
The index change induced by two-photon absorption of green light in Ge-doped optical fiber is partly anisotropic. We review the experimental facts that form the basis for a physical model of bleachable oriented defects. We also describe how a density matrix formalism, based on a simili three-level system, can be used to determine the tensorial properties of the photoinduced index change.
The different phenomena related to photoinduced self-organization in optical fiber are reviewed, from photoinduced absorption and refraction changes, to index grating formation and harmonic generation. Some pertinent questions regarding the origin and the physics of these effects are raised.