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Graphene devices for ultrafast laser science

Event Details

Event Dates: 

Thursday, April 11, 2013 - 12:00pm

Seminar Location: 

  • Duane Physics Room D142

Speaker Name(s): 

Thomas Schibli

Speaker Affiliation(s): 

CU Boulder
Seminar Type/Subject

Scientific Seminar Type: 

  • Condensed Matter Seminar

Event Details & Abstract: 

Graphene, a single atomic layer of sp2 hybridized carbon, has joined an exclusively small list of materials that will receive research funding well over a billion euros within this decade in anticipation of countless practical applications that will be nourished by the astonishing electronic, optical and mechanical properties of this truly two-dimensional material. While many of these applications are of particular interest to industrial applications, I will focus on two selected applications that are of interest to the ultrafast optics and precision measurement community: ultra-broadband saturable absorption and electro-optic modulation.The predominant application of graphene in ultrafast laser science is mode-locking of fiber and solid-state lasers. In the past few years dozens of graphene-Q-switched or mode-locked systems have been published with pulse durations ranging from 18 μs to sub-100 fs [1]. Graphene is seemingly attractive for this task due to its natural sub-100 fs recovery time, its extremely broadband operating regime (from ~1 THz to ~1 PHz), and the ease of use of this novel material compared to its epitaxially grown counterpart, the semiconductor saturable absorber mirror (SESAM). Synthetic graphene can be produced in small research labs without the large upfront investments required for III-V facilities, which greatly adds to the attractiveness of this material. However, graphene saturable absorbers have major drawbacks that were not well documented in early literature. I will discuss our findings [2,3] and how they tie in with most recent publications.Our group’s unique contribution to the world of graphene is an active electro-optic device, which enables direct active stabilization of lasers and optical frequency combs to unprecedented levels [4,5]. The underlying physics in these devices is the doping-induced changes of optical absorption, which greatly benefits from the gap-less, dispersion free band structure of graphene. The ability to continuously tune the Fermi level by electric field doping allows the construction of broad-band electro-optic absorption modulators. In this talk I will review the physics and the construction such devices and also briefly discuss why such devices enable much wider control-bandwidths in solid-state and fiber lasers compared to the state-of-the art approaches.