Research
Keisuke Goda's research focuses on the development of novel platform technologies for a diverse range of biomedical and defense applications. His education and research background lie in the fields of precision measurement, biomedical imaging, communication technology, microfluidic biotechnology, biophysics, and ultrafast optics. Specifically, he is currently working on the development of novel high-throughput methods, techniques, and instruments for multi-parameter analysis, screening, manipulation, and elimination of large heterogeneous populations of cells. Applications of such technologies include drug discovery, neuroscience, regenerative medicine, global health, food science, environmental science, and medical diagnostics and therapeutics, impacting advanced research, industrial, and clinical settings. The following is a list of his ongoing and previous research projects:High-Throughput Blood Screening
Conventional high-throughput blood analyzers such as flow cytometers and Coulter counters are unable to detect rare cell types in blood due to their high false positive rate. Important rare cell types in blood include hematopoietic stem cells, antigen-specific T cells, fetal cells in maternal blood, and circulating tumor cells. I am currently developing an optoelectronic system to detect such rare cells with high throughput yet high specificity and sensitivity. Such a system will hold great promise for noninvasive real-time medical diagnostics and therapeutics.Serial Time-Encoded Amplified Microscopy (STEAM)
STEAM is a new type of imaging modality for continuous real-time observation of fast dynamical phenomena such as shockwaves, chemical dynamics in living cells, neural activity, laser surgery, and microfluidics. STEAM maps the spatial information (image) of an object into a serial time-domain data stream and simultaneously amplifies the image in the optical domain. It captures the entire image with a single-pixel photodetector, not by a CCD or CMOS camera. With the optical image amplificaiton, STEAM overcomes the fundamental trade-off between sensitivity and frame rate - a predicament that affects virtually all optical imaging systems. As a result, STEAM can achieve ~10 MHz frame rate and ~100 ps shutter speed, enabling observation of rapid processes in physics, chemistry, and biology. I am currently working on application of STEAM to various problems in science and medicine.[1] K. Goda, K. K. Tsia, and B. Jalali, "Serial time-encoded amplified imaging for real-time observation of fast dynamic phenomena," Nature 458, 1145 (2009)
[2] K. Goda, K. K. Tsia, and B. Jalali, "Amplified dispersive Fourier-transform imaging for ultrafast displacement sensing and barcode reading," Applied Physics Letters 93, 131109 (2008)
Optical Pre-Amplification for High-Speed Microscopy
Fast real-time optical sensors are indispensable tools for pattern-recognition seen in fingerprint matching and LIDAR as well as for sensing and imaging in biological applications such as multiphoton and laser-scanning fluorescence microscopy. The central requirement for real-time operation is a signal integration time that is much shorter than the time scale of changes in the dynamic process. This requirement is very difficult to achieve because of the fundamental trade-off between sensitivity and speed; at high scan rates, fewer photons are collected during each integration time, leading to the loss of sensitivity. Optical amplification prior to photon-to-electron conversion overcomes this funtamental trade-off and hence achieves high-speed detection without sacrificing detection sensitivity. We have demonstrated, for the first time, Raman amplification in a single-mode fiber at wavelengths near 800 nm. This approach can potentially enable fast real-time optical sensing and imaging in the wavelength band that benefits from both low water absorption and the availability of high-power Ti:Sapphire lasers.[1] K. Goda, A. Mahjoubfar, and B. Jalali, "Demonstration of Raman gain at 800 nm in single-mode fiber and its potential application to biological sensing and imaging," Applied Physics Letters 95, 251101 (2009)
Simultaneous Microscopy and Microsurgery
Spectral-shower encoded confocal microscopy and microsurgery (SECOMM) is an endoscope-compatible single-fiber-based device that performs simultaneous confocal microscopy and high-precision laser microsurgery. The method is based on mapping of two-dimensional sample coordinates onto the optical spectrum and allows us to perform two-dimensional imaging and microsurgery without any mechanical movement of the probe or the sample. The technology holds promise for creating highly miniaturized endoscopes for applications such as brain tumor, pediatric, and endovascular surgeries where high-precision, small, and flexible probes are required.[1] K. K. Tsia, K. Goda, D. Capewell, and B. Jalali, "Simultaneous mechanical-scan-free confocal microscopy and laser microsurgery," Optics Letters 34, 2099 (2009)
Amplified Dispersive Fourier-Transform Spectroscopy
Dispersive Fourier-transform spectroscopy is a new type of ultrafast spectroscopic measurement technique based on the process known as dispersive Fourier transform. Dispersive Fourier transform is an optical process in which the spectrum of an optical pulse is mapped into a temporal waveform using group-velocity dispersion. As a result, dispersive Fourier-transform spectroscopy operates at ~MHz scan rate - a few orders of magnitude faster than conventional CCD-based spectrometers and mechanically scanning monochromators. This technique can also be applied to optical coherence tomography to achieve ~MHz axial scan rate.[1] K. Goda, D. R. Solli, K. K. Tsia, and B. Jalali, "Theory of amplified dispersive Fourier transformation," Physical Review A 80, 043821 (2009)
[2] K. Goda, D. R. Solli, and B. Jalali, "Real-time optical reflectometry enabled by amplified dispersive Fourier transformation," Applied Physics Letters 93, 031106 (2008)
Quantum Enhancement in Gravitational Wave Detectors
The quantum nature of the electromagnetic field imposes a fundamental limit on the sensitivity of optical precision measurements such as spectroscopy, microscopy and interferometry. The so-called quantum limit is set by the zero-point fluctuations of the electromagnetic field, which constrain the precision with which optical signals can be measured. In the world of precision measurement, laser-interferometric gravitational-wave detectors are the most sensitive position meters ever operated, capable of measuring distance changes of the order of 10^-18 m r.m.s. over kilometre separations caused by gravitational waves from astronomical sources. The sensitivity of currently operational and future gravitational-wave detectors is limited by quantum optical noise. The quantum noise can be reduced by injecting a squeezed state of light into the output port of the gravitational wave detector.[1] K. Goda, O. Miyakawa, E. E. Mikhailov, S. Saraf, R. Adhikari, K. McKenzie, R. Ward, S. Vass, A. J. Weinstein, and N. Mavalvala, "A quantum-enhanced prototype gravitational-wave detector," Nature Physics 4, 472 (2008)
[2] K. Goda, E. E. Mikhailov, O. Miyakawa, S. Saraf, S. Vass, A. Weinstein, and N. Mavalvala, "Generation of a stable low-frequency squeezed vacuum field with periodically-poled KTiOPO4 at 1064 nm," Optics Letters 33, 92 (2008)
Detection of Gravitational Waves
Gravitational waves are ripples in spacetime whose existence was predicted by Albert Einstein in his theory of general relativity. Gravitational waves are generated by accelerating masses just as electromagnetic waves are produced by accelerating charges. The direct detection of gravitational waves will further verify general relativity and open an entirely new window onto the universe. LIGO, which stands for Laser Interferometer Gravitational-Wave Observatory, is a large astrophysics experiment attempting to detect gravitational waves. Measurable emissions of gravitational waves are expected from binary systems (collisions and coalescences of neutron stars or black holes), supernovae of massive stars, and stochastic gravitational wave background produced by the birth of the universe.[1] K. Goda, the LIGO Collaboration, and the VIRGO Collaboration, "An upper limit on the stochastic gravitational-wave background of cosmological origin," Nature 460, 990 (2009)
[2] Y. Chen, A. Pai, K. Somiya, S. Kawamura, S. Sato, K. Kokeyama, R. L. Ward, K. Goda, and E. E. Mikhailov, "Interferometers for displacement-noise-free gravitational-wave detection," Physical Review Letters 97, 151103 (2006)
[3] K. Goda, D. Ottaway, B. Connelly, R. Adhikari, N. Mavalvala, and A. Gretarsson, "Frequency resolving spatiotemporal wavefront sensor," Optics Letters 29, 1452 (2004)