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Guest Lecture: "Electronically Tuneable THz Quantum Cascade Laser" (Dr Subhasish Chakraborty, University of Manchester)

On Monday 20 August Dr Subhasish Chakraborty (University of Manchester) will visit the Department and will give a talk in the Barlow Room (Room 807) at 2pm to which all interested are invited. The abstract for the talk is given below.
When Aug 20, 2012
from 02:00 PM to 04:00 PM
Where Barlow Room, Roberts Building, UCL
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A transverse computer-generated hologram (CGH) can be used to diffract light and provide flexible control of incident radiation by steering it to any point in a projected image plane. The number of resolvable points in the image projection plane is a function of the CGH’s pixel count. A longitudinal CGH (LCGH), in contrast, instead of steering light toward fixed spatial points, allows digital control in the frequency domain. This is of particular interest in the context of tunable lasers, with an LCGH offering two important degrees-of-freedom: 1) It provides high-resolution wavevector or k‑space resolution within the Brillouin zone; 2) It enables definition or modification of the reflectivity at each resolvable k‑point, so attaining a target spectral response. The flexibility of an LCGH approach has been demonstrated by achieving purely electronic tuning in a single‑section terahertz (THz) quantum cascade laser (QCL). Such tuneable single-frequency devices will enable the high power (1 – 100 mW) and compact nature of THz QCLs to be used more easily for spectroscopic applications, such as remote sensing, spectral analysis, and both security and medical imaging.