Generation of Arbitrarily Patterned Pulse Trains in the THz Range by Spectral Synthesis of Optical Combs

Isao MOROHASHI  Takahide SAKAMOTO  Norihiko SEKINE  Tetsuya KAWANISHI  Akifumi KASAMATSU  Iwao HOSAKO  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E98-C   No.8   pp.793-798
Publication Date: 2015/08/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E98.C.793
Type of Manuscript: Special Section PAPER (Special Section on Microwave Photonics)
Category: MWP Subsystem
Keyword: 
optical comb,  Mach-Zehnder modulator,  terahertz,  ultra-wideband,  

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Summary: 
We demonstrated generation of arbitrarily patterned optical pulse trains and frequency tunable terahertz (THz) pulses by spectral synthesis of optical combs generated by a Mach-Zehnder-modulator-based flat comb generator (MZ-FCG). In our approach, THz pulses were generated by photomixing of a multi-tone signal, which is elongated pulse train, and a single-tone signal. Both signals were extracted from a comb signal by using optical tunable bandpass filters. In the case of optical pulse train generation, the MZ-FCG generated comb signals with 10 GHz-spacing and 330 GHz-width, which was converted to a 2.85 ps-width pulse train by chirp compensation using a single-mode fiber. By combining the MZ-FCG with a pulse picker composed of a 40 Gbps intensity modulator, divided pulse trains and arbitrarily bit sequences were successfully generated. The single-mode light was extracted by an optical bandpass filter and the band-controlled pulse train was extracted by an optical bandpass filter. By photomixing them, a THz pulse was successfully generated. In the case of THz pulse generation, by photomixing a single-tone and a multi-tone signals extracted by tunable bandpass filters, THz pulses with a center frequency of 300 GHz was successfully generated. Furthermore, frequency tunability of the center frequency was also demonstrated.