What is a SESAM?

The SESAM device for passive modelocking was invented by Prof. Ursula Keller.

Semiconductor saturable absorber mirror (SESAM)

SESAMs have made key contributions to the performance of ultrafast solid-state lasers and their improvements. The SESAM devices are a family of optical devices that allow for very simple, self-starting passive modelocking of ultrafast solid-state lasers.

The SESAM design is a multi-disciplinary effort involving key understanding of both semiconductor and solid-state laser physics, and has resulted in new unprecedented performance improvements in terms of pulse widths, average power, and repetition rates in these lasers.

These performance improvements and the implementation of the SESAM device also has allowed for many new practical application and commercialization of these lasers, increasing their use not only in R&D environments but also in medical, industrial, metrology and communications applications.

More precisely, the SESAM device is based on the nanotechnology of semiconductor epitaxial material deposition, allowing control of layers of material down to the sub-nanometer accuracy. This allows for very precise optical devices with practically complete control of the key design parameters – magnitude and phase of the optical absorption and reflection, plus adjustment of key parameters such as the saturation fluence (energy level where the device saturates) and its temporal response (how fast the absorber recovers).

The optical characteristics of the modulation depth, saturation fluence, and non-saturable loss are key for proper laser performance. They are used as a direct input into theoretical guidelines to guarantee suppression of unwanted Q-switching instabilities with relatively simple expressions relating controllable design features of the laser and the SESAM device such that Q-switched modelocking can be avoided. Once the device design is optimized, a semiconductor wafer fabrication allows these devices to be produced economically, and ultimately in large volumes.

Review Articles:
2010 20 years of SESAM: DownloadRef. [300] (PDF, 750 KB)vertical_align_bottom
2005 Low saturation fluence SESAM: DownloadRef. [228] (PDF, 593 KB)vertical_align_bottom
2003 Compact ultrafast lasers and applications: DownloadRef. [185] (PDF, 298 KB)vertical_align_bottom
1996 SESAM concept: DownloadRef. [62] (PDF, 394 KB)vertical_align_bottom

2012 20 years anniversary since the invention of the first SESAM device.
Invited plenary talk at ALT 2012 in Gwatt, Switzerland.
DownloadPDF copy of talk available for download (PDF, 13.1 MB)vertical_align_bottom