Florian Pilat , Nikola Opačak , Sandro Dal Cin , Andreas Windischhofer , Etienne Giraud , Sargis Hakobyan , Richard Maulini , Antoine Muller , Pierre Jouy , Pitt Allmendinger , Benedikt Schwarz
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引用次数: 0
Abstract
The linewidth enhancement factor (LEF) of quantum cascade lasers (QCLs) is an important parameter, recently tightly linked to many phenomena that occur in this type of laser — from self-starting frequency combs to the emergence of solitons. The dynamic processes involved act at frequencies similar to the roundtrip frequency of the lasers (typically GHz), reflected in the high-frequency component of the LEF. Its value in QCLs is predicted to increase under laser operation with increasing light intensity, as the stronger gain saturation effectively increases the spectral gain asymmetry. Here, we investigate the hot-cavity LEF of a free-running frequency comb far above the laser threshold and at high frequencies, employing shifted wave interference Fourier transform spectroscopy (SWIFTS). Our measurements confirm an increasing LEF with laser current, which is supported by numerical simulations. From the spectral slope of the LEF we can extract further important parameters, such as the gain peak frequency and the decoherence time of the laser transition, which is tightly linked to the available gain bandwidth.
期刊介绍:
Optics & Laser Technology aims to provide a vehicle for the publication of a broad range of high quality research and review papers in those fields of scientific and engineering research appertaining to the development and application of the technology of optics and lasers. Papers describing original work in these areas are submitted to rigorous refereeing prior to acceptance for publication.
The scope of Optics & Laser Technology encompasses, but is not restricted to, the following areas:
•development in all types of lasers
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•developments in new photonics and optical concepts
•developments in conventional optics, optical instruments and components
•techniques of optical metrology, including interferometry and optical fibre sensors
•LIDAR and other non-contact optical measurement techniques, including optical methods in heat and fluid flow
•applications of lasers to materials processing, optical NDT display (including holography) and optical communication
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