Polarization-sensitive photodetectors

E c at 297 K. (b) Spectral responsivity Rjet of a Schottky diode photodetector processed from sample IX for E c and E c. The inset depicts a schematic of the device and the measurement geometry. 

---

The in-plane polarization anisotropy can be enhanced by anisotropic strain. This can be achieved by choosing a nonpolar orientation with an appropriate substrate. In the extreme case of M-plane GaN on liAl02, the degree of linear polarization can be increased to its maximum value of one for all three transitions between the three uppermost valence bands (VBs) and the conduction band (CB), corresponding to complete linear polarization for all three transitions. This optical anisotropy can be observed in transmission (absorption) and reflection, as well as photoluminescence (PL) and photoreflectance (PR) spectroscopy. It can therefore be used for polarization filtering, polarization-sensitive photodetectors (PSPDs), and polarized light emitters. For anisotropically strained C-plane GaN films on (1120) sapphire, the in-plane polarization properties have been previously reported in Refs. 1-3. 

Until recently, previous studies for continuous monitoring of hepatic function with ICG utilized the absorption mode. However, new studies demonstrate that the highly sensitive fluorescence technique can equally be used [148-150]. In addition to high sensitivity, in-depth analysis of the emission, excitation and polarization properties of fluorescence spectroscopy furnishes additional functional information about the dye molecule. In this system, the fluorescence profile emanating from the clearance of injected biocompatible dye is monitored with a small photodetector. Fig. 8 shows the in vivo fluorescence detection apparatus developed for continuous monitoring of organ functions [147,148]. 

In Eq. (14.1), I is fluorescent intensity the subscript letters, V for vertical and H for horizontal, represent the polarization direction of the two polarizers on the excitation and emission light path, respectively and the ratio, ZHV/IhH) calibrates for the difference in the emission channel s sensitivity towards vertical and horizontal polarized components. Anisotropy, r, can be measured by either L-format or T-format. In the L-format, all four fluorescence intensities, Zw, h11, f iv. and ZHh> are measured using a single channel of a photodetector so that each intensity needs to be measured separately. If the fluorimeter has two emission channels then anisotropy can also be measured in a T-format, which allows fluorescence intensities pairs, Ivv//Vi i or If iv // ii i, to be measured simultaneously via the two emission channels. Thus, measurements in the T-format are faster than in the L-format. 

An ultrafast time-resolved near- and mid-IR absorption spectrometer was designed to achieve high sensitivity, ultrafast time resolution, and broad tunability in the near- and mid-IR regions (see Fig. 2). The details of this spectrometer are described elsewhere (9). Briefly, MbCO was photolyzed with a linearly polarized laser pulse, whose polarization direction was controlled electronically by a liquid crystal polarization rotator. The photolyzed sample was probed with an optically delayed, linearly polarized IR pulse whose transmitted intensity was spectrally resolved with a monochromator and detected with either a Si photodiode (near-IR RilO cm-1 bandpass) or a liquid nitrogen-cooled InSb photodetector (mid-IR 3 cm-1 bandpass). To measure the sample transmission, this signal was divided by a corresponding signal from a reference IR pulse... 

---