Optical sampling by laser cavity tuning

Thomas Hochrein,Norman Krumbholz,Martin Koch,Michael Mei,Rafal Wilk,Ronald Holzwarth

doi:10.1364/oe.18.001613

Abstract

Most time-resolved optical experiments rely either on external mechanical delay lines or on two synchronized femtosecond lasers to achieve a defined temporal delay between two optical pulses. Here, we present a new method which does not require any external delay lines and uses only a single femtosecond laser. It is based on the cross-correlation of an optical pulse with a subsequent pulse from the same laser. Temporal delay between these two pulses is achieved by varying the repetition rate of the laser. We validate the new scheme by a comparison with a cross-correlation measurement carried out with a conventional mechanical delay line.

Highlights

The invention of modelocked femtosecond lasers in 1991 has enabled a large variety of time resolved experiments
Other research fields which rely on femtosecond pulses with a variable time delay in between are optical coherence tomography [5], coherent control [6] and terahertz time-domain spectroscopy [7,8]
We have introduced Optical Sampling by CAvity Tuning (OSCAT), a new technique which enables time-resolved experiments with a single laser and without any external delay lines

Summary

Introduction

The invention of modelocked femtosecond lasers in 1991 has enabled a large variety of time resolved experiments. Mechanical delay lines are employed to temporally delay one pulse with regard to the other [9,10,11,12] These include linearly moving stages, or rotating mirrors or fibre-stretchers [13,14]. The technique relies on two synchronized pulsed femtosecond lasers which are slightly detuned in the repetition rate [15,16,17] This technique is known as asynchronous optical sampling (ASOPS). Such systems need a complex control for the stabilization of the pulse repetition rates of both lasers. The new technique allows for very robust, compact and cost-efficient experimental setups in the above mentioned fields We call this technique optical sampling by cavity tuning (OSCAT)

Theoretical foundations

Experimental demonstration

Conclusion and outlook