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Scientist develop a broadband quantum-dot frequency-modulated comb laser

Scientist develop a broadband quantum-dot frequency-modulated comb laser

Posted Date: 2023-07-28
Scientist develop a broadband quantum-dot frequency-modulated comb laser
The quantum-dot (QD) laser is a promising platform for the era of each frequency-modulated (FM) and amplitude-modulated (AM) combs. The mechanisms of those combs are totally different and decided by the acquire dynamics of the laser. The AM comb formation requires a sluggish acquire, which may be achieved by making use of a low injection present to the QD laser’s acquire part. The FM comb formation depends on a quick acquire to generate large Kerr nonlinearity and four-wave mixing. This may be realized by merely controlling the biases on the acquire and the saturable absorber. Engineering of the Kerr nonlinearity contributes to a big enchancment within the 3-dB optical bandwidth to 2.2 THz. Credit score: by Bozhang Dong, Mario Dumont, Osama Terra, Heming Wang, Andrew Netherton, and John E. Bowers

Because the conception of the laser frequency comb within the late Nineteen Nineties, it has revolutionized the exact measurement of frequency and time. Past their preliminary use in optical clocks and precision spectroscopy, optical frequency combs (OFCs) have exhibited sturdy potential for numerous purposes, together with ultraviolet and infrared (IR) spectroscopy, distant sensing, optical frequency synthesis, and high-speed optical communications.

Nevertheless, the sturdy optical pulses delivered by an amplitude-modulated (AM) OFC will not be favorable to dense wavelength-division multiplexing (DWDM) methods through which many microring modulators are deployed. It's because the excessive instantaneous energy of optical pulses would end in sturdy thermal nonlinearities.

Alternatively, the formation of a broadband OFC depends on cautious engineering of the group velocity dispersion (GVD) of the waveguide, which is difficult for platforms the place the GVD is principally decided by the fabric. Therefore, the system measurement, weight, energy consumption, and price (SWaP-C) of OFCs have to be improved for the usage of OFCs in business.

In a brand new paper revealed in Gentle: Science & Purposes, a workforce of scientists, led by Professor John Bowers from the Institute for Power Effectivity, College of California, Santa Barbara, USA, has developed a frequency-modulated (FM) comb based mostly on superior quantum-dot (QD) laser. A correct laser cavity design allows a report 3-dB optical bandwidth of two.2 THz within the Telecom O-Band.

The channel spacing is as massive as 60 GHz, which is useful for eliminating the channel crosstalk in knowledge transmission. Extra apparently, this quasi-continuous-wave FM comb doesn't ship sturdy optical pulses, which is favorable to an built-in DWDM system.

By making the most of the QD laser, the broadband FM comb is generated from a 1.35 mm-long and a couple of.6 um-wide laser cavity, together with a excessive wall-plug effectivity of over 12%. In comparison with different built-in OFC applied sciences, the reported FM comb based mostly on QD laser displays a superior SWaP-C, which is an answer being pursued by each academia and business.

The outstanding materials properties of QD make it a promising platform for FM comb era. The ultrafast acquire dynamics enable for big Kerr nonlinearity and four-wave mixing, which makes the QD laser a greater candidate for FM comb era within the Optical Communication Band than the standard quantum-well diode lasers.

Importantly, this reported strategy permits us to enhance the optical bandwidth with out the necessity for cautious engineering of the waveguide dispersion. This achievement is realized by the engineering of Kerr nonlinearity, which may be merely managed by a voltage utilized to the saturable absorber part of the laser. As such, this strategy reduces the challenges within the fabrication course of. These scientists touch upon their achievements on this work:

“That is an evolution of pondering. The primary mode-locked laser was demonstrated in 1963, large progress has been made since then. It was once thought {that a} mode-locked laser should ship sturdy optical pulses due to its AM (amplitude-modulation) nature. Nevertheless, we display that it doesn’t need to. The FM (frequency-modulated) mode-locked laser is experiencing a renaissance. It's its nature to ship a broadband and flat-topped spectrum together with a quasi-continuous-wave emission.”

“Regardless of the demonstration of FM combs in mid-infrared quantum cascade lasers, the FM nature of near-infrared QD mode-locked lasers was not totally exploited. We try to know it and apply the FM mode-locked laser to high-speed PICs (photonic built-in circuits) for knowledge facilities,” they added.

“The offered approach addresses the problems that an OFC encounters on PICs and it's appropriate with the mature CMOS business. Our findings give novel insights into the development of FM mode-locked lasers for PICs. This breakthrough may open a brand new venue for the following era of PICs for 5G/6G communication, synthetic intelligence, and autonomous driving,” the scientists say.

Offered by Chinese language Academy of Sciences