Fermionics (United States)

In June 2005, a newly develop long wave Focal Pane Array (FPA), based on photo-voltaic technology was delivered to the Defense Research & Development of Canada (DRDC). This development was part of technological Demonstration program that was founded by the DRDC. This paper will describe the FPA configuration along with its performance assessment configured in the Air PIRATE FTIR spectrometer. Air PIRATE is an airborne version of the hyper spectral spectrometer used by the Canadian Defense for target identification, as well as chemical agent identification.

The advanced planar ion-implantation-isolated heterojunction process, which utilizes the benefits of both the boron implantation and the heterojunction epitaxy techniques, has been developed and used to produce longwave and very longwave HgCdTe focal plane arrays in the 320v256 format. The wavelength of these arrays ranges from 10.0-17.0μm. The operability of the longwave HgCdTe arrays is typically over 97%. Without anti-reflection coating and with a 60° FOV cold shield, the D* of the 10.0μm array is 9.4x10¹⁰cm x (Hz)^1/2 x W^-1 at 77K. The 14.7μm and 17.0μm very longwave HgCdTe array diodes have excellent reverse characteristics. The detailed characteristics of these arrays are presented.

Harmonic signals reflected from electroabsorption modulators are measured and analyzed as a function of modulator bias. The second-harmonic signal exhibits a dip close to the bias where the maximum of RF link gain occurs, over a significant optical power range. Using an equivalent circuit analysis we show this is caused by the inherent electroabsorption effect. The second-harmonic signal can be exploited for dynamic self-bias control of electroabsorption modulators in analog fiber-optic links.

relationships. The two absorption characteristics serve as basis ftmctions to form a linear combination,which, if properly chosen, results in a more linear transfer characteristic. Mixing of the two effects isaccomplished with a single-mn metal-organic vapor-phase epitaxial (MOWE) growth and processinga rib-loaded waveguide structure. A cross-sectional schematic of the combined structure is shown in

A novel approach is proposed for controlling the bias of an electroabsorption waveguide modulator for maximum radio-frequency (RF) gain in analog fiber-optic links. It is based upon the correlation between the RF gain and the modulator DC photocurrent. It is found that, under various operating conditions, the modulator bias at which the modulator DC photocurrent experiences the largest change with incremental bias, coincides with the bias for the maximum RF gain. This approach eliminates the need for an external tracking photodiode, and can be useful in bias controls of a modulator array.

By finding the bias voltage V one can track the optimum bias, VRF-max, for maximum RF efficiency. This concept suggests a new approach to dynamically control the modulator bias for maintaining maximum RF link gain under changing operation conditions. In this work we show that V dynamically tracks VRFmax and thus can be used for controlling the modulator bias voltage for maximum RF efficiency. InGaAsP-InP Franz-Keldysh effect waveguide modulators are used in the measurements.

A Franz-Keldysh effect InGaAsP electroabsorption waveguide device is utilized as a high-frequency, high-linear dynamic range modulator and photodetector. The dual-function modulator/photodetector can be useful in compact transmit/receive front end antenna architectures. Adjusting the electrical bias to the reverse-biased p-i-n diode, either efficient optical modulation or detection is demonstrated. As an electroabsorption modulator, a fiber optic link with a -17.4-dB RF loss and a 124-dB-Hz/sup 4/5/ suboctave spurious-free dynamic range is obtained with electrical biases in the 2 to 3 V range. As a waveguide photodetector, a 0.45-A/W fiber coupled responsivity, photocurrents up to 20 mA, and an output second-order intercept of +34.5 dBm are achieved at 7-V electrical bias.

The spurious-free dynamic range (SFDR) of an InGaAsP-InP Franz-Keldysh effect (FKE) waveguide modulator is studied. Low-biasing the FKE modulator is shown to enhance the SFDR by 22 dB with a 3-dB optical power penalty. Polarization-independent RF operation is also obtained with low bias. At 2 mA photocurrent, the simulated narrowband and broadband SFDR are, respectively, 127 dB and 104 dB in a 1-Hz bandwidth. The measured result projects a narrowband SFDR of 129 dB-Hz/sup 4/5/ at this photocurrent.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photoassisted molecular‐beam epitaxy (PAMBE) has been employed to grow a series of undoped and doped CdTe films. In and Sb were used as n‐type and p‐type dopants, respectively. The PAMBE‐grown epilayers exhibit outstanding electrical, optical, and structural properties as determined by van der Pauw Hall‐effect, low‐temperature photoluminescence, and double‐crystal x‐ray rocking curve measurements, respectively.

Photoassisted molecular-beam epitaxy (PAMBE), in which the substrate is illuminated during film growth has been successfully employed to prepare n-type CdTe:In and p-type CdTe:Sb films. The n-type layers exhibit large electron mobilities at low temperatures. Field effect transistors have been fabricated from selected CdTe:In layers grown by PAMBE which show good device characteristics. The p-type CdTe:Sb films exhibit bright photoluminescence of excitonic origin at low temperatures. At 300 K, hole mobilities of 81 cm2/V s and carrier concentrations in excess of 1018 cm−3 have been achieved by the PAMBE technique.