About

The Goal of UVQuanT

Lasers are the heart of today’s quantum science and technology. Since their first invention they have been a flourishing research area and in a few decades have found application in an enormous variety of fields, eventually populating many aspects of our everyday life, also outside of the research laboratory. Since the beginning, there has been a natural push towards extending the accessible frequency range of coherent radiation, eventually covering the whole infrared (IR), visible (VIS), and ultraviolet (UV) spectrum. The large energy and momenta of UV photons offers enormous potential for novel applications. However, for the same reason, deep technological challenges remain before they can be used effectively in science and technology. UVQuanT will tackle this challenge by developing the necessary industrial and scientific expertise to realise new-era, cost-effective lasers and laser optics for the UV and DUV region, positioning the EU as the front-runner in this technology. UVQuanT will focus on new ways of increasing the production of coherent radiation in the UV and DUV region, developing and testing lower cost, more rugged and practical solutions, and will test these novel systems in a range of experiments targeting quantum technology applications. Combining the talent and expertise of industrial and academic partners, UVQuanT will build strong relationships for establishing a path for next-generation quantum technologies.

Accessing the DUV through frequency conversion

Frequency conversion in nonlinear optical materials (NLO) is an invaluable tool for generating laser light in regions of the electromagnetic spectrum where gain media lasers are limited or non-existent. The efficiency of frequency conversion is nonlinear with the intensity of the fundamental light, and for a high CW conversion efficiency it is necessary to place the NLO material inside an optical enchancement resonator. Inside the resonator the circulating optical power can be more than two orders of magnitude larger than the input power greatly increasing the conversion efficiency.

UVQuanT will use two methods of frequency conversion known as Second Harmonic Generation (SHG), where the frequency (wavelength) of input light is doubled (halved), and Sum Frequency Generation (SFG) where two frequencies are added to produce a third higher frequency output, to produce CW sources of DUV laser light.

Laser systems

Vertical-external-cavity surface-emitting-lasers (VECSELs) are a pumped semiconductor laser capable of producing very high powers (several W) in the near-infrared (NIR). They provide high tunability due to the broad gain medium, and narrow linewidth with a birefringent filter, etalon and piezoelectric mounted output coupler allowing for precise frequency selection.

VECSELs can be intracavity frequency doubled by including an LBO crystal within the laser cavity, reducing the complexity that comes from successive SHG systems for generating light in the DUV.

SHG Systems

The generation of light with an SHG enhancement resonator is done using a NLO crystal, for example LBO or BBO, placed in a "bow tie" resonator, where the optical power of the input light circulating in the resonator is increased more than two orders of magnitude, significantly increasing the efficiency of the conversion. The frequency doubled light is coupled out of the cavity through a frequency dependent output where it can be used.

The resonators can be stabilised with a PID loop by measuring the polarization of light reflected from the input window, and adjusting the length of the cavity with a mirror mounted to a piezoelectric transducer, maintaining maximum output power of the frequency doubled light.

Generating DUV light down to 205 nm is currently performed by starting with an infrared laser and doubling it twice with successive SHG stages.

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