The worldwide first all-fiber THz time-domain spectrometer for operation at 1.5 microm is presented. Applications up to 3 THz are demonstrated. Key devices are photoconductive antennas based on novel LT InGaAs/InAlAs multi-layer structures.

A compact and low-cost continuous wave terahertz spectrometer operating at an optical wavelength of 1.5 μm is presented. The spectrometer employs high power distributed feedback (DFB) laser diodes in integrated "butterfly" packages. No further optical amplification of the beating signal is required. An integrated photodiode antenna with an output power of 5 μW at 500 GHz is used as efficient terahertz emitter. Employing low-temperature grown (LT-) InGaAs/InAlAs photoconductive receivers as coherent detectors, SNR values of the terahertz power up to 75 dB are attained at an integration time of 300 ms. Accurate characterization of the thermal tuning behavior of the DFBs and precise thermal control yield an absolute accuracy of 1 GHz and a resolution of better than 5 MHz, without any on-line monitoring of the optical frequency. Due to the high frequency resolution no delay line is needed to vary the terahertz phase.

A fiber-assembled CW THz System operating at 1.5 microm is presented. High speed telecom photodiodes integrated with planar THz antennas serve as THz emitters with power up to 10 microW. Photoconductive antennas based on LT InGaAs/InAlAs multi-layer structures allow coherent detection. The system operates in a wide frequency range of 0.1 -1.6 THz.

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All-optical clock recovery from 40-Gb/s nonreturn-to-zero (NRZ) pseudorandom binary sequence data streams based on self-pulsating lasers is presented. A compact preprocessing circuit is utilized to convert an NRZ signal to a pseudoreturn-to-zero sequence before injecting into the optical clock. It comprises a semiconductor optical amplifier followed by a periodical wavelength-division-multiplexing demultiplexer filter. A stable sinusoidal clock signal with a root-mean-square jitter below 700 fs is detected at the output of the self-pulsating laser within data dynamic range of more than 8 dB. The performance of the all-optical clock recovery scheme is investigated by varying the bit rates between 39.81 and 43.02 Gb/s as well as for various wavelengths in the C-band