Yuta Mizumoto

Dispersion tailoring of a crystalline whispering gallery mode microcavity for a wide-spanning optical Kerr frequency comb

We fabricated a crystalline whispering gallery mode microcavity by using a computer-controlled ultraprecision cutting process to control the cavity cross section. We used a numerical simulation to show that a wide-spanning optical Kerr frequency comb is generated by tailoring the dispersion of a crystalline whispering gallery mode microcavity. To control the dispersion, we designed the cross-sectional shape of the device and fabricated it by using ultraprecision cutting. Both the measured value and the numerical result show that the microcavity has an anomalous dispersion over one octave.

Bi-material crystalline whispering gallery mode microcavity structure for thermo-opto-mechanical stabilization

We fabricated a calcium fluoride (CaF2) whispering gallery mode (WGM) microcavity with a computer controlled ultra-precision cutting process. We observed a thermo-opto-mechanical (TOM) oscillation in the CaF2 WGM microcavity, which may influence the stability of the optical output when the cavity is employed for Kerr comb generation. We studied experimentally and numerically the mechanism of the TOM oscillation and showed that it is strongly dependent on cavity diameter. In addition, our numerical study suggests that a microcavity structure fabricated with a hybrid material (i.e. CaF2 and silicon), which is compatible with an ultra-high Q and high thermal conductivity, will allow us to reduce the TOM oscillation and stabilize the optical output.

Dispersion tailoring of a crystalline whispering gallery mode microcavity for optical Kerr frequency comb generation

The generation of an optical Kerr comb in whispering gallery mode (WGM) microcavities has been investigated for applications in frequency metrology, precise spectroscopy, and signal processing. Optical Kerr combs are generated via parametric frequency conversion, thus a high quality factor (Q) is essential for lowering the threshold power, and this can be achieved with crystalline microcavities in, for example, calcium fluoride (CaF 2 ) because of the low absorption coefficient of this material. An optical Kerr comb with a wide span is needed to obtain frequency stabilization with the f-2f self-referencing method, which requires an anomalous dispersion [1]. We used a computer controlled precise cutting machine to fabricate a dispersion controlled CaF 2 microcavity with an anomalous dispersion to obtain exactly the same dispersion as we obtained in the numerical simulation.

Soliton pulse formation in a calcium fluoride whispering gallery microcavity without frequency sweeping

We study a way of achieving a soliton pulse from a CaF2 microcavity. We fabricated a dispersion controlled CaF2 cavity and also numerically developed a method to generate soliton pulses without sweeping the input laser.

Basic study on ductile-mode grinding of optical glass lenses with rubber bonded diamond wheels

Large aperture lenses with high surface quality are demanded for professional imaging products such as single-lens reflex cameras and astronomical telescopes. Large aperture optical lenses are shaped by ultra-precision grinding and finished by prolonged polishing. However, the prolonged polishing process leads to deterioration of the form accuracy. In order to reduce the amount of polishing, ductile-mode ultra-precision grinding is demanded. In this study, a rubber bonded wheel, which has a low elastic modulus, is used for grinding of spherical glass BK7, and influence of the hardness of the rubber bonded wheel and abrasive chip thickness on brittle fracture and surface roughness are experimentally investigated.

Dispersion tailoring of a crystalline whispering gallery mode microcavity for octave-spanning Kerr frequency comb

The generation of an optical Kerr comb in whispering gallery mode (WGM) microcavities has been investigated for applications in frequency metrology, precise spectroscopy, and signal processing. Optical Kerr combs are generated via parametric frequency conversion, thus a high quality factor (Q) is essential for lowering the threshold power, and this can be achieved with crystalline microcavities in, for example, calcium fluoride (CaF2) because of the low absorption coefficient of this material. An optical Kerr comb with a wide span is needed to obtain frequency stabilization with the f-2f self-referencing method, which requires an anomalous dispersion [1]. We used a computer controlled precise cutting machine to fabricate a dispersion controlled CaF2 microcavity with an anomalous dispersion to obtain exactly the same dispersion as we obtained in the numerical simulation.