This work presents a highly sensitive hybrid-integrated optical receiver with a custom designed linear transimpedance amplifier (TIA). The choice of the circuit and diode technology, considering the impact of process parameters on the optical sensitivity and the input referred noise current, are elaborated. The TIA has been designed in a 55-nm complementary metal oxide semiconductor process and was combined with a commercial InGaAs/InP PIN-diode. Measurements resulted in a transimpedance of 9.2 kΩ and a bandwidth of 1.4 GHz. The optical sensitivity of the hybrid receiver is −27.45 dBm for 2 Gbps, with a wavelength of 1550 nm and a bit error rate of 10 − 9. The input referred root mean square (RMS) noise current results in 110 nA. The fabricated chip has an area of 410 μm × 410 μm and a power consumption of 31 mW at a 1 V supply voltage. The performance of the designed TIA is able to match other designs used in high sensitivity applications such as continuous variable quantum key distribution or optical wireless communication, while consuming significantly less power and having a smaller chip area.
A highly sensitive monolithic optical receiver, applicable in optical fiber and wireless communication is presented. The proposed chip is capable of processing data rates of up to 10 Mb / s and offers compatibility to standard CMOS logic by creating full 3.3-V output swing. The photodetector of the system is carried out as a large-area fully integrated avalanche photodiode with a diameter of 800 μm and a high responsivity to red light with a wavelength of 675 nm. The receiver features pseudo differential signal processing with offset cancellation feedback to achieve desensitization to background light irradiation usually appearing with optical wireless communication. Additionally, common-mode feedback was implemented to prevent pulse width distorted output signals. Measurements at 2.5, 5, and 10 Mb / s reveal high sensitivities of −50.4, −47.65, and −42.7 dBm, respectively, for BER < 10 − 9 in dark conditions. For the design, a 0.35-μm CMOS process was chosen.
A pulsed (4.4 ns pulse length) frequency doubled Nd:YAG laser, operating at 10 Hz, was used to generate Raman
scattering from samples at a distance of 12 m. The scattered light was collected by a 6 inch telescope and the Raman
spectrum recorded using an Acton SP-2750 spectrograph coupled to a gated ICCD detector. To extend the potential
applications further, employing a spatial offset between the point where the laser hit the sample and the focus of the
telescope on the sample, enabled collection of Raman photons that were predominantly generated inside the sample and
not from its surface. This is especially effective when the content of concealed objects should be analysed. Raman
spectra of H2O2 in a 1.5 mm thick, fluorescent HDPE plastic bottle were recorded at a distance of 12 m. From the
recorded spectra it was possible to determine the H2O2 concentration in the concentration range from 2-30%. Stand-off
Raman spectra of eleven potentially dangerous chemicals (commercial and improvised explosives) were recorded at a
distance of 100 m.
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