Deep UV to NIR frequency combs via cascaded harmonic generation in a silica nanowire using nanojoule pulse energies

Abstract

Compact, turnkey frequency combs in the deep ultraviolet (UV) to near-infrared (NIR) wavelength region are important for applications ranging from ultralow power spectroscopy and quantum memory to light–atom interactions. Translation of an IR (1550 nm) comb from a compact mode-locked laser (MLL) to visible wavelength region, using cascading of optical nonlinearities, provides the simplest way to realize an on-demand deep UV to NIR comb. However, the translation of an IR comb to the visible region extending from deep UV to NIR has been difficult to achieve in a single device. We exploit chirped pulsed compression and dispersion engineering to report the simultaneous generation of second- (780 nm), third- (520 nm) and sixth-order (260 nm) harmonics of a 1560 nm MLL in a 10 mm long silica nanowire using nanojoule pulse energies. RF spectrum measurements of the 520 nm signal show that the 82 MHz frequency comb at 1560 nm is translated to visible. The use of a single-mode fiber nanotaper and turnkey mode-locked IR laser creates a hybrid platform that provides deep UV to NIR comb and enables applications in quantum optics through trapping and probing of atoms using the evanescent field of nanotaper.