Editing Quantum dot laser (section)

{{Short description|Semiconductor laser that uses quantum dots as the active laser medium}}
A '''quantum dot laser''' is a [[semiconductor laser]] that uses [[quantum dot]]s as the [[active laser medium]] in its light emitting region. Due to the tight confinement of [[charge carrier]]s in quantum dots, they exhibit an electronic structure similar to atoms. Lasers fabricated from such an active media exhibit device performance that is closer to [[gas laser]]s, and avoid some of the negative aspects of device performance associated with traditional semiconductor lasers based on bulk or [[quantum well]] active media. Improvements in [[modulation bandwidth]], [[lasing threshold]], [[relative intensity noise]], linewidth enhancement factor and temperature insensitivity have all been observed. The quantum dot active region may also be engineered to operate at different wavelengths by varying dot size and composition. This allows quantum dot lasers to be fabricated to operate at wavelengths previously not possible using semiconductor laser technology.<ref>{{Cite web|url=https://www.fujitsu.com/global/about/resources/news/press-releases/2004/0910-01.html|title=Fujitsu, University of Tokyo Develop World's First 10Gbps Quantum Dot Laser Featuring Breakthrough Temperature-Independent Output - Fujitsu Global}}</ref> One challenge in the further advances with quantum dot lasers is the presence of multicarrier [[carrier generation and recombination|Auger processes]] which increases the nonradiative rate upon population inversion.<ref name="melnychuk">{{Cite journal |last=Melnychuk |first=Christopher |last2=Guyot-Sionnest |first2=Philippe |date=2021-02-24 |title=Multicarrier Dynamics in Quantum Dots |url=https://pubs.acs.org/doi/10.1021/acs.chemrev.0c00931 |journal=Chemical Reviews |volume=121 |issue=4 |pages=2325–2372 |doi=10.1021/acs.chemrev.0c00931 |issn=0009-2665|url-access=subscription }}</ref> Auger processes are intrinsic to the material but, in contrast to bulk semiconductors, they can be engineered to some degree in quantum dots at the cost of reducing the radiative rate. Another obstacle to the specific goal of electrically-pumped quantum dot lasing is the generally weak conductivity of quantum dot films.

Devices based on quantum dot active media have found commercial application in medicine ([[laser scalpel]], [[optical coherence tomography]]), display technologies (projection, [[laser TV]]), spectroscopy and telecommunications. A 10 [[Gbit/s]] quantum dot laser that is insensitive to temperature fluctuation for use in [[optical data communication]]s and [[optical telecommunication|optical networks]] has been developed using this technology. The laser is capable of high-speed operation at 1.3 μm wavelengths, at temperatures from 20&nbsp;°C to 70&nbsp;°C. It works in optical data transmission systems, optical [[local area network|LAN]]s and [[Metropolitan area network|metro-access systems]]. In comparison to the performance of conventional [[strained quantum-well laser]]s of the past, the new quantum dot laser achieves significantly higher stability of temperature.

Newer, so called "Comb lasers" based on quantum dot lasers have been found to be capable of operating at wavelengths of ≥ 80&nbsp;nm and be unaffected by temperatures between -20&nbsp;°C and 90&nbsp;°C, and allow higher accuracy with reduced fluctuations and less [[relative intensity noise]].<ref>{{Cite web|url=https://www.innolume.com/quantum-dots/|title = Quantum dot laser technology}}</ref><ref>{{Cite web|url=https://www.innolume.com/innoproducts/comb-laser/|title = Comb laser &#124; Optical Frequency Combs}}</ref>

In development are colloidal quantum dot lasers, which would use quantum confinement to change the optical properties of the semiconductor crystals (≤ 10&nbsp;nm in diameter) through solution-based rearrangements of quantum dots.<ref>{{cite journal |last1=Park |first1=Young-Shin |last2=Roh |first2=Jeongkyun |last3=Diroll |first3=Benjamin T. |last4=Schaller |first4=Richard D. |last5=Klimov |first5=Victor I. |title=Colloidal quantum dot lasers |journal=Nature Reviews Materials |date=May 2021 |volume=6 |issue=5 |pages=382–401 |doi=10.1038/s41578-020-00274-9 |bibcode=2021NatRM...6..382P |osti=1864315 |s2cid=231931231 }}</ref><ref>{{cite journal |last1=Kagan |first1=Cherie R. |last2=Bassett |first2=Lee C. |last3=Murray |first3=Christopher B. |last4=Thompson |first4=Sarah M. |title=Colloidal Quantum Dots as Platforms for Quantum Information Science |journal=Chemical Reviews |date=10 March 2021 |volume=121 |issue=5 |pages=3186–3233 |doi=10.1021/acs.chemrev.0c00831 |pmid=33372773 |s2cid=229715753 }}</ref>