Yoshiro Nomoto

Phase-modulating lasers toward on-chip integration

Controlling laser-beam patterns is indispensable in modern technology, where lasers are typically combined with phase-modulating elements such as diffractive optical elements or spatial light modulators. However, the combination of separate elements is not only a challenge for on-chip miniaturisation but also hinders their integration permitting the switchable control of individual modules. Here, we demonstrate the operation of phase-modulating lasers that emit arbitrarily configurable beam patterns without requiring any optical elements or scanning devices. We introduce a phase-modulating resonator in a semiconductor laser, which allows the concurrent realisation of lasing and phase modulation. The fabricated devices are on-chip-sized, making them suitable for integration. We believe this work will provide a breakthrough in various laser applications such as switchable illumination patterns for bio-medical applications, structured illuminations, and even real three-dimensional or highly realistic displays, which cannot be realised with simple combinations of conventional devices or elements.

Robust photodetector for vacuum ultraviolet laser light

An evacuated photocell including a pair of planar interdigitated electrodes fabricated on a sapphire substrate is proposed. Photocurrent in the photocell was found to be originated from both a photoemission effect on the gold cathode and an internal photoelectric effect in the sapphire substrate. Because of the robust nature of the sapphire substrate and the gold electrodes, the photocell reliably tolerated more than 105 shots of fluorine laser pulses as strong as 0.13 J/cm2/pulse on the 7×7 mm2 active area. The photocell was successfully employed for measuring the pulse shapes of F2 laser light with a temporal resolution shorter than 6 ns.

Evaluation of Laguerre-Gaussian beam generated with integrable phase-modulating surface-emitting lasers

We demonstrated direct surface-emitting of Laguerre–Gaussian beams with wavefront modulated lasers. This integrable phase-modulating surface-emitting lasers has potential to emit arbitrarily configured beam patterns without requiring any optical elements or scanning devices. The fabricated devices are on-chip-sized, making them suitable for integration. We introduce a phase-modulating resonator in a semiconductor laser, which analogically behaves as phaseonly holograms, kinoform, to allow the concurrent realization of lasing and phase modulation. Particularly, this is promising in the use for free-space optical communications due to the fact that coaxial propagation of orbital angular momentum (OAM) properties with different OAM mode states are mutually orthogonal.