CLEO-PR 2013 Takumi Kato

TuC1-5: Chirped-pulse up conversion of mid-infrared pulses with four-wave difference frequency generation in gases
difference frequency generation in gases molecular laboratory
The mid-infrared region is the molecular vibration band of many molecules and is used in the field of spectroscopy. However, detector performance in the mid-infrared region is poor. Highly sensitive MCT detectors (mercury, cadmium, and tellurium semiconductor devices) operate only at liquid nitrogen temperatures. DTGS detectors, which can operate at room temperature, have a slow response time and low signal-to-noise ratio, making it difficult to detect weak infrared radiation. In this research, infrared light transmitted through a material is multiplied by pump light, converted to a different wavelength, and measured with high sensitivity using a visible light detector. Although this idea itself has a precedent, wavelength conversion has conventionally been performed using nonlinear crystals. Although the bandwidth that can be converted is limited due to phase-matching effects, Xe gas is used as the nonlinear medium in this study. This enables conversion at the octave level. By processing the detected converted light with a computer, infrared spectroscopy can be performed with high sensitivity.

TuF3-5: High Resolution Molecular Spectroscopy Assisted by an Optical Frequency Comb Fukuoka Univ.
There have been many studies using optical combs, but the overall picture of what they can do and what they cannot do is not clear. In this study, high-resolution molecular spectroscopy was performed using an optical comb, and the fact that this kind of research is being presented at academic conferences indicates that there is still room for further development. The experimental image is simple: sweep a wavelength-tunable laser, inject it into a molecule of I2, and observe its absorption spectrum. However, at the same time as the sweep, we interfered with an optical comb locked to the GPS and observed the beats of the tunable laser and the optical comb. By continuously observing the beats of and , we can determine the absolute frequency of the tunable laser. It is said that high resolution can be achieved by passing the data through different bandpass filters and processing them. Notably, this bandpass-filter technique has been used in Del'Haye et al, "Frequency comb assisted diode laser spectroscopy for measurement of microcavity dispersion," Del'Haye et al, "Frequency comb assisted diode laser spectroscopy for measurement of microcavity dispersion," Del'Haye et al. Photon. 3, 529 (2009).

Tul4-1: Next Generation Silicon Photonics Cornell Univ.
1: High speed modulation silicon ring
He talked about whether it is the Q-value or FSR that limits optical signal modulation by silicon rings. He said that the conventional limit was 20 Gbps, but that further increases could be expected by creating a mechanism that allows thermal changes to be applied to only one-quarter of the ring.

2: Connections with electronics using amorphous silicon
Much of Lipson's talk focused on how to merge silicon photonics with existing electronics. When silicon is grown on top of electronics, it must be grown at low temperatures so as not to destroy semiconductor devices. Amorphous silicon satisfies this requirement. A nitride layer on top of the amorphous silicon makes it possible to combine electronics with ring resonators and other devices. Amorphous silicon connects the electronode and the nitride, and it is said that a waveguide structure can be created by laser annealing. Amorphous silicon is generally considered to have poor optical properties due to the presence of cracks, but as long as the waveguide diameter is as thin as 200 nm, it is not affected by cracks.

3: Multimode Photonics
It seems that the times are shifting to multimode, with visions of communication with different information on the first-order and second-order modes. For this purpose, he is working on determining the waveguide structure using the concept of transformation optics.

WF2-3 Fiber Laser Driven Mid-Infrared Frequency Combs, Ingmar Hartl
Currently, the longest optical comb that can be generated is in the 2-μm band. Since most of the molecular vibrations exist in the mid-infrared band, many studies are being conducted to generate optical combs in the 2.5μm to 15μm band. SC, DFG/SFG, OPO, Microcavity, QCL, etc. are possible methods for generating optical combs, but considering stability and operability, it is wise to use a fiber laser as the core. In this study, we use a fiber laser to generate a mid-infrared optical comb. For the fiber laser, a Tm laser that generates 1.95 μm is used. This technology is commonly used in the communication wavelength band around 1.5 μm, but it has not been studied in other wavelength bands. In this study, too, it was essential to appropriately arrange Tm fiber lasers, OP-GaAs, and ZGP crystals suitable for the mid-infrared region.