As the core of modern optics, particularly integrated optics, high-quality pulse and coherence laser source are always important focuses of academic circle and industrial circle. Under the support of CAS Class B special project of strategic pilot technology "Large-sale Photon Integrated Chip", XIOPM’s micro-nano optics and photon integration team has made series important progresses in on-chip integrated light source.
First, the team achieved multiple-frequency (1~15) stable laser pulse source on chip with 49GHz as the fundamental frequency. The research achievement was published in SCI Optics I journal ACS Photonics on July 19 with the title of "Repetition Rate Multiplication Pulsed Laser Source Based on a Micro-ring Resonator". It designs different laser parameters and takes advantages of interaction among gains of the light field, non-linearity and chromatic dispersion in laser cavity, to generate various pulse laser sources, which have contributed to rich fruits in academic and commercial fields. Facing higher demands for laser pulse source in fields of ultrahigh speed optical clock, high-speed optical communication technology, microwave photonics, spectral measurement and astronomical optical frequency comb, XIOPM, using its own on-chip micro-ring resonator, based on the dissipation four-wave mixing effect, has realized 49GHz-fundamental-frequency stable laser pulse output, effectively lowering high-phase noise due to Schawlow and Townes limitation compared with ultrashort pulse. Meanwhile, using the on-chip laser mode selection mechanism, the team has achieved 49~735GHz multiple rate laser pulse, and broken the limitation of laser cavity’ free spectrum range on repeated frequency.
Second, the team made an important breakthrough in the technology of Fourier transformation limit ultra-narrow on-chip mode-locked laser. Traditional mode-locked technology is often used to realize ultra-short pulse. Researchers use mode-locked technology more for broadening frequency spectrum bandwidth to realize ultrashort, subpicosecond-level even attosecond-level laser pulse, while the mode-locked laser of ultra-narrow on-chip nanosecond pulse within Fourier transformation limit is more difficult to be realized. This kind of laser, with narrow frequency spectrum bandwidth, can be widely used in fields of spectroscopy measurement, sensor, coherence optical communication and quantum optics. Research Fellow of XIOPM, through cooperation with multiple foreign units and using non-linear-amplification loop reflection mirror, realized ultra-narrow spectrum’s integrated passive mode-locked laser. In the achievement, the core loop reflection mirror adopts XIOPM’s peculiar micro-ring resonator of low loss, high refraction coefficient difference and high Q value. The time domain FWHM of the laser pulse output by the laser is 4.31ns, average output optical power is about 2.5mW, peak power is up to 60mW, output amplitude RMS＜2.3%,and spectrum width 104.9MHz, lower by 2 orders compared with the traditional research. The research achievement was published in Nature Photonics in 2017.
The above-mentioned research achievements are series breakthroughs of XIOPM’s micro-nano optics and photon integration team after cross polarized photon pair generation(Nature communications, 2015）, on-chip multi-photon entanglement state generation(Science, 2016）, visible light optical frequency comb realization(Laser & Photonics Review, 2016）and high-dimension light quantum chip (Nature, 2017）, and lay an important foundation for development of light quantum integrated chip in the future. (By the Department of Technology and Management, the Laboratory for Transient Optics and Photon Technology)
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