Journal Club 2016 | Tanabe Photonic Structure Group

Journal Club

By fiscal year (April-December)

Fiscal Year 2016

Presentation Details:

Unlike Raman and Brillouin lasers, Lipron lasers are produced by the energy exchange between light and capillary waves. Capillary waves are intrinsic to liquids and oscillate using surface tension as a restoring force. We measured the interaction between light and capillary waves using an octane droplet trapped in water with optical tweezers as an opto-capillary resonator. The results suggest that opto-capillary cooling at room temperature toward the ground state is expected.

Presentation Details:

Continuous tuning of the squeezed light level generated by two silicon nitride ring resonators with built-in micro-heaters was achieved. Variations in the squeezed level ranging from 0.9 dB to 3.9 dB were observed by varying the coupling state with the waveguide. These results are expected to play an important role in applications where appropriate squeezed levels are required.

Presentation Details:

Future information technologies such as ultrafast data recording, quantum computation, and spintronics will require unprecedentedly fast spin control by light. Intense terahertz pulses can couple to spins on the energy scale inherent to magnetic excitation. In this work we investigate a new mechanism of nonlinear terahertz-spin coupling mediated by electric dipoles, which is much stronger than the linear Zeeman coupling to terahertz magnetic fields. We demonstrate that terahertz resonant excitation of electronic orbital transitions in a typical antiferromagnet thulium orthoferrite (TmFeO 3 ) modulates the magnetic anisotropy of the ordered Fe 3+ spins, producing coherent spin oscillations with large amplitude. The mechanism is inherently nonlinear, can be tuned by spectral shaping of the terahertz waveform, and the efficiency exceeds Zeeman torque by an order of magnitude. Since orbital states dominate magnetic anisotropy in all transition metal oxides, the control scheme demonstrated here is expected to be applicable to many magnetic materials.

Presentation Details:

A pair of two parallel 1D photonic crystal resonators, one pair for each of the pump and probe beams, was used to fabricate a structure in which each is influenced by the other via mechanics oscillations. The advantage of this structure is that the optical paths of the pump and probe beams are different. The observed vibrational frequencies of the optomechanics from the experimental results are in good agreement with the results of the FEM calculations. Experimental results have also been obtained where the pump light dynamically changes the transmission spectrum of the photonic crystal resonator corresponding to the probe light, which is expected to be applied to oscillators.

Presentation Details:

A supercontinuum with a center spread of 1550 nm in a single octave has been realized using an InGaP waveguide fabricated on a silicon substrate. The advantage of this technology is that it can be realized with lower power consumption and smaller area than previous studies, which also contributes to the high coherence of the generated spectrum.

Presentation Details:

An all-pass-microring-Bragg-grating based coupled resonance system that exhibits EIT-like transmission characteristics is proposed and demonstrated. The coupling between a "microring resonator" and a "Fabry-Perot resonator composed of two sections of Bragg grating" between optical waveguides induces an EIT-like spectrum. This system has a simple configuration of a microring resonator and a bus waveguide, which has strong advantages in terms of fabrication errors. The results showed an extinction rate (ER) of 12 dB, FWHM of 0.077, and Q-value of 20200, in good agreement with simulations.

Presentation Details:

Optical frequency conversion and control is a very important technology for many applications. In this study, we demonstrate that frequency conversion via Bloch oscillation is possible using a dynamically modulated ring resonator. It is also shown that frequency conversion in a single direction is possible by periodically modulating the ring resonator. These results demonstrate the possibility of optical frequency manipulation using a dynamic resonator system.

Presentation Details:

Single-photon frequency control technology is essential for quantum communications, but conventional methods based on nonlinear optical effects have been difficult to put into practical use due to noise and bandwidth problems. In this paper, we fabricate a single-photon frequency shifter based on optomechanics and demonstrate that it can modulate up to 150 GHz without adding noise with a conversion efficiency close to unity.

Presentation Details:

Quantum teleportation allows for the faithful transfer of quantum states between remote nodes in a network, enabling innovative information processing applications. This has motivated a vast amount of research activity. However, until now, quantum teleportation experiments using independent quantum light sources, entanglement delivery prior to Bell state measurement (BSM), and feedforward operations simultaneously have not been realized, even in a laboratory environment. In this work we address this challenge and report on the construction of a 30 km fiber optic quantum network deployed over a 12.5 km area. The network is robust against real-world noise due to active stabilization methods, which makes it possible to achieve quantum teleportation that satisfies all the factors simultaneously. Both quantum state and process tomography measurements, as well as independent statistical hypothesis testing, confirm the quantum nature of quantum teleportation on this network. This experiment is an important step toward realizing a global "quantum Internet" in the real world.

Presentation Details:

The rotational symmetry of the whispering gallery mode makes it difficult to apply as a directional light source. To break the rotational symmetry, deforming the shape of the resonator has been proposed, but these methods have the disadvantage that the Q-value of the resonator is greatly reduced. In this paper, we present a method to realize directional light emission while maintaining the Q-value by freely adjusting the mode characteristics of the whispering gallery mode using transform optics.

Presentation Details:

Since ring lasers have clockwise (CW) and counterclockwise (CCW) modes, there is a problem that laser beams with unstable intensity are output in both directions on the silicon waveguide. In this paper, we show that the ratio of CW to CCW can be manipulated by employing a locally deformed structure of the ring laser, and demonstrate that a laser beam with stable intensity can be obtained from only one direction of the silicon waveguide through experiments using the actually fabricated ring laser.

Presentation Details:

In recent years, optical fluid dynamics has become an important technique in bioanalysis. In particular, lasers based on optical hydrodynamics are considered to have much higher sensitivity and imaging resolution than lasers based on fluorescence, but this field has not been well studied. In this study, near-infrared dye called indocyanine green was used for imaging the major components of human blood. In addition, this is the first time that indocyanine green has been used in the raging of human blood.

Presentation Details:

Current lens manufacturing processes limit optical performance due to the limited size and shape of the lenses. Timo Gissibl and colleagues used a femtosecond laser direct-write system to 3D print a multi-lens system with a size of approximately 0.1 mm. The multi-lens system consists of multiple singlet lenses (single lenses) combined into a composite lens structure within a container-like support, and is printed at a rate of several centimeters per second.

Presentation Details:

Not only is the optical clock a powerful tool for important basic research, but it is also being considered for use in redefining the SI unit "second" because of its accuracy and stability more than one order of magnitude better than the cesium atomic clock. However, an important obstacle to this transition is the unreliability of optical clocks, which makes the continuous realization of timescales impractical. In this work, we show how this situation can be resolved and demonstrate that a photometric timescale can be established that surpasses that of the cesium atom spring clock.

Presentation Details:

A laser filament is a stable state caused by the equilibrium between the convergence of the Kerr effect from intense laser pulses and the divergence from plasma generation. In this study, laser filamentation at kHz repetition rate is demonstrated for the first time in the mid-infrared band.
Furthermore, filaments in the mid-infrared band are expected to be useful for sensing various chemical substances, and we have confirmed the absorption spectroscopy of CO2 in the atmosphere.

Presentation Details:

An X-ray detector using a single crystal of methylammonium lead bromide (MAPbBr3) perovskite was fabricated for the first time. The minimum detectable X-ray dose was 0.5 µGy air s-1, which is four times more sensitive than the α-Se X-ray detector, which is known as a very sensitive X-ray detector. These results are expected to be useful in medical and security inspection. In the presentation, we will focus on the fabrication of the detector.

Presentation Details:

Real-time Fourier transform of signals (RTFT) is a fundamental concept that allows Fourier analysis faster than the limits of conventional digital signal processing engines. In optics, RTFTs are typically used to excite large amounts of group velocity dispersion, where it is important to map the frequency spectrum of the signal along the time domain. However, the optical frequency resolution of this technique is typically limited to gigahertz or better, hindering applications such as real-time spectroscopy, ultrafast detection, imaging, sensing, and especially optically assisted RF signal generation and processing. We have experimentally implemented the new RTFT concept using a frequency-shifted feedback laser and achieved a frequency resolution of approximately 30 kHz and a time-bandwidth product in excess of 400.

Presentation Details:

Bubbles generated by filamentation in water using femtosecond lasers are expected to have applications such as microchannel switching and cell sorting. In this study, we directly observed the movement of bubbles generated by filamentation under a microscope and observed that the bubbles moved along the water flow generated by filamentation. The angle between the direction of movement of the bubbles and the direction of laser propagation changed depending on the distance between the filament and the bubbles, and the process of convection in the water caused by filamentation was clarified.

Presentation Details:

We have developed a new platform that combines an optomechanical resonator holding light at a wavelength of 1550 nm and phonons at a frequency of 2.4 GHz with photonic and phononic waveguides, and demonstrated that by using RF and light waves to excite or read out the mechanical modes, we can convert coherent signals between the optical and We have demonstrated that coherent signals can be converted between the optical, RF, and mechanical domains by using RF and light waves to excite or read out the mechanical modes.

Presentation Details:

Some of the most precise measurements ever made, from attosecond time-domain spectroscopy to frequency comb measurements, have been made possible by mode-locked lasers. However, such extreme precision hides the complexity of the underlying mode-locking dynamics. This complexity is particularly pronounced in the emergence of mode-locked states, which are essentially singular non-repetitive transitions. Although many of the details of mode-locking are well understood, conventional spectroscopy cannot resolve the initial dynamics in passive mode-locking on the natural nanosecond time scale of a single pulse period. In this study, we have captured the pulse-resolved spectral evolution of a femtosecond pulse train from the initial fluctuations and continuously recorded it over about 900,000 periods. We directly observe critical phenomena on time scales of tens to thousands of round-trips, including the emergence of broadband spectra, accompanying wavelength shifts, and transient interference dynamics expressed as auxiliary pulse mode-locking. Our results, made possible by time-stretching transformations, have potential implications for laser design, ultrafast diagnostics, and nonlinear optics.

Presentation Details:

We investigated the chaos created by nonlinearly coupled optomechanics. Two major points became clear from the investigation: first, chaotic states are transferred by mechanical pathways, and second, the presence of chaotic states can improve the signal-to-noise ratio. On the day of the presentation, I will explain in detail how what we used in this study fits into the category of stochastic resonance.

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What is Journal Club?
This is an open lecture series held in Tanabe Photonic Structures Laboratory. Students who are graduate students or above will survey papers related to optics and related technologies such as photonics, materials, bioscience, etc., and explain them in an easy-to-understand manner.

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Attendance is free, regardless of whether you are inside or outside of the university. The seminar will be held periodically, so if you are interested in any of the topics, please feel free to attend. No notice is required to attend, but we will prepare materials if you contact us in advance.

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