Richard Epstein
University of New Mexico
First demonstration of laser cooling in a solid; rare-earth spectroscopy; cryogenic optical refrigerators.
Cooling · coherentIn memoriam
Mansoor Sheik-Bahae
1956 – 2023
Carnot 2026 is dedicated to Mansoor Sheik-Bahae, who passed away in July 2023, aged 67. Born in Isfahan, a descendant of the seventeenth-century polymath Sheikh Bahāʾi, Mansoor came to the United States to study electrical engineering, taking his doctorate at SUNY Buffalo in 1987. He joined CREOL in its founding year and moved to the University of New Mexico in 1994, rising to Distinguished Professor — the highest honor UNM gives its faculty — and becoming the first director of its Optical Science and Engineering program.
With Eric Van Stryland and colleagues, Mansoor invented the Z‑scan: one beam, a moving sample, a detector, and from it the sign and magnitude of a material’s optical nonlinearity. It remains the standard measurement, and the two of them shared Optica’s R. W. Wood Prize for it in 2012. He then found a link that had been thought impossible — Kramers–Kronig relations are linear, so they ought not to connect nonlinear quantities. The way through was to linearize the problem by treating nondegenerate absorption, two photons of different frequency, which made nonlinear refraction predictable from two-photon absorption. A Fellow of Optica and of SPIE, he was also a senior member of the IEEE.
In 1995 Mansoor began working with Richard Epstein on cooling solids with light, and led that effort for the next twenty-seven years, directing the Consortium for Laser Cooling in Solids from 2004 to 2022. The group established Yb:YLF as the material the field now builds on, and in 2022 cooled a load to 125 K. He worked out the theory of radiation-balanced lasers, and his group built the first ones; others carried it from there to the first cooling of Yb-doped silica. And when he pulled the mirror stack out of a semiconductor disk laser, it opened a field — the MECSEL — that now reaches as far as sodium guide stars.
Cooling a semiconductor was something he was deeply passionate about seeing, and he never got the chance. His co-authors called it his unfulfilled dream. One session of this workshop goes straight at that problem. Another continues his work on radiation-balanced lasers. A deep thinker, Mansoor never stopped pondering the fundamental limits of noise, entropy and engine efficiency. He would have loved to be at this workshop with all of us. His presence is missed dearly!
Selected works
- 1989Z-scanM. Sheik-Bahae, A. A. Said, T.-H. Wei, D. J. Hagan and E. W. Van Stryland, IEEE J. Quantum Electron. 26, 760–769 (1989)
- 1991Kramers–Kronig and nonlinear refractionM. Sheik-Bahae, D. C. Hutchings, D. J. Hagan and E. W. Van Stryland, IEEE J. Quantum Electron. 27, 1296 (1991)
- 2007Optical refrigeration, reviewM. Sheik-Bahae and R. I. Epstein, Nature Photonics 1, 693–699 (2007)
- 2010Laser cooling to cryogenic temperaturesD. V. Seletskiy, S. D. Melgaard, S. Bigotta, A. Di Lieto, M. Tonelli and M. Sheik-Bahae, Nature Photonics 4, 161–164 (2010)
- 2015Mirrorless semiconductor disk laser — the MECSELZ. Yang, A. R. Albrecht, J. G. Cederberg and M. Sheik-Bahae, Opt. Express 23, 33164–33169 (2015)
- 2018First all-solid-state optical cryocooler — an infrared sensor cooled to 135 KM. P. Hehlen, J. Meng, A. R. Albrecht, E. R. Lee, A. Gragossian, S. P. Love, C. E. Hamilton, R. I. Epstein and M. Sheik-Bahae, Light: Science & Applications 7, 15 (2018)
- 2019First radiation-balanced disk lasersZ. Yang, J. Meng, A. R. Albrecht and M. Sheik-Bahae, Opt. Express 27, 1392–1400 (2019)
- 2020Theory of radiation-balanced lasersM. Sheik-Bahae and Z. Yang, IEEE J. Quantum Electron. 56, 1000109 (2020)
- 2022A load cooled to 125 KJ. L. Kock, A. R. Albrecht, R. I. Epstein and M. Sheik-Bahae, Opt. Lett. 47, 4720–4723 (2022)
- 2022Semiconductor sodium guide-star sourceM. Zhang et al., Opt. Express 30, 42470–42479 (2022)
