July 2022
Spotlight Summary by Marco Piccardo
Ultra-broadband flat-top quantum dot comb lasers
A chip-scale broadband frequency comb emitting in the telecom range useful for multiplexed communications was demonstrated, thanks to advances in the design of quantum dot lasers. In wavelength-division multiplexing each tooth of the comb acts as a distinct channel that can be modulated to transmit information. A flat-top comb spectrum is convenient so that the different channels have similar amplitudes. Moreover, for each channel to carry a high bandwidth, the modulation must be at high frequency. This sets the requirement of a large spacing among the comb teeth—at least 100 GHz—to avoid crosstalk.
To generate a widely-spaced comb there are two options. The first is to use a short cavity—corresponding to a high repetition rate—but this results in low power output and large optical linewidth. J.-Z. Huang et al. demonstrate in this work another approach, based on a technique known as colliding pulse mode-locking, dividing a long cavity in multiple short sections separated by saturable absorbers. This results in large emission power, small linewidth and satisfies the requirement of 100 GHz comb spacing. By combining four of these comb sources, each operating at a different temperature to cover a different spectral range, this approach holds promise for large bandwidth data transmission (up to 4.8 Tbit/s) for the future telecom optical interconnects.
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To generate a widely-spaced comb there are two options. The first is to use a short cavity—corresponding to a high repetition rate—but this results in low power output and large optical linewidth. J.-Z. Huang et al. demonstrate in this work another approach, based on a technique known as colliding pulse mode-locking, dividing a long cavity in multiple short sections separated by saturable absorbers. This results in large emission power, small linewidth and satisfies the requirement of 100 GHz comb spacing. By combining four of these comb sources, each operating at a different temperature to cover a different spectral range, this approach holds promise for large bandwidth data transmission (up to 4.8 Tbit/s) for the future telecom optical interconnects.
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Article Information
Ultra-broadband flat-top quantum dot comb lasers
Jing-Zhi Huang, Zi-Tao Ji, Jia-Jian Chen, Wen-Qi Wei, Jia-Le Qin, Zi-Hao Wang, Zhi-Yuan Li, Ting Wang, Xi Xiao, and Jian-Jun Zhang
Photon. Res. 10(5) 1308-1316 (2022) View: Abstract | HTML | PDF