Workshop  ·  First independent edition  ·  2026

Carnot 2026 — Photonic Heat Engines

A two-day workshop on optical refrigeration, radiation-balanced lasers, and high-power laser source development.

A laser run backwards is a refrigerator. Everything interesting happens in between.

Dates24–25 October 2026
VenuePAIS, University of New Mexico
CityAlbuquerque, New Mexico
FormatSingle track, discussion-focused

Registration is open — attendance is free. Register here. Questions: carnot.workshop@gmail.com.

The premise

Entropy is a design variable, not a bookkeeping detail.

A laser pump is a single narrowband mode; the fluorescence it drives is broadband and leaves in every direction. That difference in entropy between the two light fields is what allows a solid to be cooled with light, and it gives a laser crystal three operating points. When lasing, the quantum defect heats it. Pumped below the mean fluorescence energy, anti-Stokes emission carries heat away — optical refrigeration. In between, the two cancel: a radiation‑balanced laser, whose gain medium carries no net heat load.

Heat limits the average power, beam quality and frequency stability of solid-state lasers. This workshop is about the regime where source design and thermal management stop being separate problems.

Carnot continues the Photonic Heat Engines community, which met for eight editions within a larger photonics meeting through 2024. This is its first independent meeting.

HEAT OUT HEAT IN Laser Quantum defect deposits heat in the crystal. Radiation-balanced laser Defect heating cancels fluorescence cooling. Optical refrigerator Anti-Stokes fluorescence carries heat away.
One material, one pump beam, three operating points. The workshop's first four sessions run along this axis — from the coldest physics to the hottest hardware.

Confirmed speakers

Everyone named here has accepted. Further invitations are out; the list will grow as they are answered. Session groupings are provisional.

Richard Epstein

Richard Epstein

Los Alamos National Laboratory (retired)

First demonstration of laser cooling in a solid; rare-earth spectroscopy; cryogenic optical refrigerators.

Opening remarks
Markus Hehlen

Markus Hehlen

Triton Photonics

Rare-earth spectroscopy; ultrapure fluoride crystals; solid-state optical refrigeration.

Rare earths
Hiroki Tanaka

Hiroki Tanaka

Leibniz Institute for Crystal Growth (IKZ), Berlin

Fluoride crystal growth; Yb-doped cooling materials; radiation-balanced laser design.

Rare earths
Peter Pauzauskie

Peter Pauzauskie

University of Washington

Laser refrigeration of nanomaterials; Yb-doped nanocrystals; nanoscale thermometry.

Rare earths
Masaru Kuno

Masaru Kuno

University of Notre Dame

Semiconductor nanostructures; single-particle spectroscopy; laser cooling of semiconductors.

Semiconductors
Matt Sheldon

Matt Sheldon

Texas A&M University

Nanophotonics and plasmonics; hot-carrier photophysics; luminescence thermodynamics.

Semiconductors
Arash Mafi

Arash Mafi

University of Kansas

Disordered and Anderson-localizing optical fibers; fiber lasers; nonlinear optics.

Radiation-balanced lasers
Peter Dragic

Peter Dragic

University of Illinois Urbana-Champaign

Optical fiber materials and glass science; Brillouin scattering; fiber laser design.

Radiation-balanced lasers
Michel Digonnet

Michel Digonnet

Stanford University

Rare-earth-doped fiber lasers, amplifiers and sensors; radiation-balanced silica fiber lasers.

Radiation-balanced lasers
Hanieh Fattahi

Hanieh Fattahi

Max Planck Institute for the Science of Light, Erlangen

Ultrafast and field-resolved optics; sun-pumped radiation-balanced lasers.

Incoherent pumping
Sushrut Ghonge

Sushrut Ghonge

Saint Mary’s College

Thermodynamics of photoluminescent cooling; cooling with incoherent and broadband light.

Incoherent pumping
Denis Seletskiy

Denis Seletskiy

University of New Mexico

Ultrafast and quantum optics; laser cooling of solids; vacuum-field fluctuations.

Opening remarks · session to be assigned
Joel Bixler

Joel Bixler

Air Force Office of Scientific Research

Program Officer, High-Energy Radiation-Matter Systems (HERMES).

Panel discussion
PC

Pengning Chao

Maxwell Labs

Invited talk from Maxwell Labs; title to be announced.

High-power sources

Support

Sponsors

Organizations interested in supporting the workshop are welcome to write to carnot.workshop@gmail.com.

Workshop sponsor

Maxwell Labs

With support from

The University of New Mexico, Department of Physics & Astronomy SELA Photonics Triton Photonics

Tentative program

Draft as of 22 September 2026. The workshop runs from 08:00 on Saturday to 15:00 on Sunday — the program closes at 14:00, and the optional laboratory tours run until 15:00, so a flight from 17:00 onwards is safe. Session themes run along the thermal axis: rare-earth cooling, semiconductor cooling, radiation-balanced lasers, then high-power sources and applications. Talks will be assigned to slots once the program is settled.

Fourteen invited talksFlash talksPoster session, with prizes Panel discussionCommunity roadmap and funding sessionLaboratory tours
PAIS 1010, the workshop room
PAIS 1010, where all of this happens. Two walls of whiteboard, one screen — talks, flash talks, posters and the panel discussion all live in this room.

Day One

Saturday 24 October
Registration, arrival, and coffee
Opening session (20 min)Welcome from the organizers, with opening remarks
I · Optical refrigeration — rare earths3 × 30 min
Talk 1
Talk 2
Talk 3
Coffee break (30 min)
II · Optical refrigeration — semiconductors2 × 30 min
Talk 4
Talk 5
Lunch (60 min)Catered on site
Workshop photograph (15 min)Everyone, outside the PAIS entrance
III · Radiation-balanced lasers3 × 30 min
Talk 6
Talk 7
Talk 8
IV · High-power sources and applications3 × 30 min + panel discussion
Talk 9
Talk 10
Talk 11
Coffee break (30 min)
Panel discussion (60 min)From laboratory demonstration to deployed hardware
V · New workFlash talks and posters
Flash talks (30 min)Two minutes and one slide — each poster presenter introduces their work
Poster session and light reception (75 min)Light refreshments — dinner follows
Coach to the restaurant (15 min)Group bus from the PAIS building, and back afterwards
Evening
Workshop dinnerPoster prizes presented

Day Two

Sunday 25 October
Registration, arrival, and coffee
VI · Pumping with incoherent light3 × 30 min
Talk 12
Talk 13
Talk 14
Coffee
Contributed talks15 min each · prize-winning students present
Community roadmap and funding strategyReporting standards for cooling performance · shared characterization · funding pathways
Working lunch
Lab tours / adjournOptional tours of UNM laboratories · the workshop ends at 15:00

Session themes

I · Optical refrigeration — rare earthsYb-doped fluorides, ultrapure crystal growth, and how far below ambient a solid can be driven.
II · Optical refrigeration — semiconductorsBulk crystals and nanostructures, luminescence quantum yield, and the barriers to net cooling.
III · Radiation-balanced lasersThe pump wavelength at which quantum-defect heating and anti-Stokes cooling cancel, so the gain medium carries no net heat load.
IV · High-power sources and applicationsThermal management at power, linewidth and frequency stability, and hardware that has to leave the bench. Closes with the panel discussion.
VI · Pumping with incoherent lightSunlight instead of a laser — sun-pumped radiation-balanced lasers, and the thermodynamics of cooling a solid with broadband light. It shares Session III’s color because it is the same physics with a different pump.
V · New workFlash talks and the poster session — students and postdocs presenting results that are still in motion.

Students and postdocs

Poster session, with prizes

Around twelve posters are expected, drawn from the speakers’ groups, from UNM’s Center for High Technology Materials, and from the national laboratories. The session has its own seventy-five-minute block in PAIS 1010 on Day One, with a light reception, introduced by flash talks in which every presenter gets two minutes and one slide.

Poster prizes, sponsored by SELA Photonics, are awarded at the workshop dinner, and the winners are invited to give short talks in Sunday’s contributed session.

Registration

Registration is open

Attendance is free. Registering tells us you are coming and lets us give the caterers a number.

  • Cost
    Free for all attendees, including the catered lunch, the poster reception and the workshop dinner.
  • Deadline
    10 October 2026. Abstracts are collected separately, in early October.
  • Posters
    Students and postdocs are especially encouraged. No abstract is needed to register — we write to poster presenters in early October. Every poster gets a two-minute flash talk, and prizes are awarded at the dinner.
  • Questions
No registration fee

Register for Carnot 2026

Three minutes. Name, affiliation, which days you are coming, dietary requirements, and whether you are bringing a poster. No abstract needed.

Open the registration form

Opens in a Google Form. No account required — you will get a copy of your answers by email, and you can edit them later if your plans change.

Venue and travel

Albuquerque, late October

The workshop meets in the Physics, Astronomy and Interdisciplinary Sciences building on the University of New Mexico main campus. Los Alamos, Sandia, the Air Force Research Laboratory and UNM's Center for High Technology Materials are all within reach of the same room — which is why the field's center of gravity has moved here.

Painters moved to New Mexico for the light. At 5,300 feet the air is thin and dry, the blue overhead is harder than seems reasonable, and shadows keep their edges. It is a fitting place to spend two days arguing about photons.

Late October is the best of it — seventies by day, forties after dark, aspen gold still holding on the Sandias, and balloons going up at dawn.

  • Venue
    Physics, Astronomy and Interdisciplinary Science (PAIS) Building
    210 Yale Boulevard NE, Albuquerque, NM 87106
    University of New Mexico main campus — northeast corner of Yale and Redondo
  • Room
    PAIS 1010 — two walls of whiteboard, a large projection screen, and a glass wall onto the inner courtyard.
  • Lodging
    Hotel Parq Central
    806 Central Avenue SE, Albuquerque, NM 87102
    Block held at the UNM rate for invited speakers and international guests
  • From the airport
    Albuquerque International Sunport (ABQ) is 10 minutes from the hotel. Hotel Parq Central runs a complimentary airport shuttle, 7:30 am–10:30 pm.
  • Hotel to PAIS
    The free 777 Express bus, or a 25-minute walk.
  • Calendar
  • Registration
    Open and free; closes 10 October 2026. Register here.
PAIS on the map Hotel Parq Central Directions, hotel to PAIS
The PAIS building at the University of New Mexico
Cholla cactus silhouetted against an orange and pink desert sunset
Cholla at sunset. The light is what brought the painters, and it is still the best argument for coming.
Chile ristras hanging above crates of fruit at a roadside stand
Ristras at a roadside stand. Red or green is not a rhetorical question here.
Cholla in the foreground with the Sandia Mountains lit gold behind
The Sandias at the end of the day, from the edge of town. The range runs the whole eastern side of the city.
Red sandstone bluff above juniper and pinyon
Red rock and juniper. The drive out of the valley in almost any direction looks like this.

The building

The PAIS atrium
The atrium. Arrival, coffee, and the conversations that happen between sessions.
The inner courtyard seen through the glass wall of PAIS 1010
The same room looks onto the inner courtyard. Late October in Albuquerque is warm enough to take the breaks outside.

If you can stay an extra day

Sandia Peak TramwayFrom the edge of the city to 10,378 feet in fifteen minutes — a rise of 3,819 feet, and the longest aerial tram in the Americas.
The Very Large ArrayTwenty-seven dishes on the Plains of San Agustin, about two and a half hours southwest. Worth the drive.
Santa Fe and Los AlamosSanta Fe is an hour north. Los Alamos, where this field began, is about ninety minutes.
“Red or green?”The official state question. It refers to chile, you will be asked it, and if you cannot decide the answer is “Christmas.”
Albuquerque seen from the crest of the Sandia Mountains
Albuquerque from the crest, 10,378 feet. This is what the fifteen minutes on the tram buys you.
Adobe structures at Taos Pueblo below a forested mountain
Taos Pueblo, inhabited for roughly a thousand years, about two and a half hours north.
Adobe wall with projecting viga beams under a deep blue sky
Adobe and vigas in Santa Fe, an hour up the interstate.
Volcanic cliff and ponderosa pines
Volcanic rock and ponderosa on the way north, toward Los Alamos.

Organizing committee

Denis SeletskiyUniversity of New Mexico
Masaru KunoUniversity of Notre Dame
Peter PauzauskieUniversity of Washington
Alejandro RodriguezPrinceton University / Maxwell Labs

Local organizing committee

Alexander AlbrechtUniversity of New Mexico
Max GardnerUniversity of New Mexico
Morteza DarvishiUniversity of New Mexico
Ghazaleh AnsariUniversity of New Mexico