Research
The Photonics Laboratory @ UCLA performs multi-disciplinary research and development in the fields of silicon photonics, microwave photonics, and biophotonics for biomedical and defense applications. Below is a list of ongoing projects.
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 real-time observation of rapid transient processes in physics, chemistry, and biology. We are currently developing a STEAM flow cytometer with ultrahigh throughput for identification and enumeration of rare cells in blood.
[1] "Serial time-encoded amplified microscopy (STEAM)," Wikipedia [2] B. Jalali, P. Soon-Shiong, and K. Goda, "Breaking speed and sensitivity limits," Optik & Photonik 2, 32 (2010) [3] B. Jalali, K. Goda, P. Soon-Shiong, and K. K. Tsia, "Time-stretch imaging and its applications to high-throughput microscopy and microsurgery," IEEE Photonics Society Newsletter 24, 11 (2010) [4] 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) [5] 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) |
Center for Integrated Access Networks (CIAN)
 The Center for Integrated Access Networks (CIAN) is a multi-institutional research effort consisting of more than several universities including UCLA. The vision of CIAN is to create transformative technologies for optical access networks where virtually any application requiring any resource can be seamlessly and efficiently aggregated and interfaced with existing and future core networks in a cost-effective manner. Analogous to the evolution over decades of today's computer laptop using massive integration of discrete electronic components, the CIAN vision would lead to the creation of the PC equivalent of the optical access network by employing optoelectronic integration to enable affordable and flexible access to any type of service, including delivery of data rates approaching 10 Gbits/s to a broad population base anywhere and at any time. We are currently developing novel methods and instruments to achieve the CIAN goal.
[1] Center for Integrated Access Networks (CIAN) [2] A. Fard, S. Gupta, B. Jalali, "Ultrahigh bandwidth sampling scope via an NI5154 and a photonic time stretch pre-processor," NIWeek Conference (2009) [3] A. Fard, S. Gupta, and B. Jalali, "Digital equalization of ultrafast data using real-time burst sampling," Optical Fiber Communication Conference / National Fiber Optic Engineers Conference (2010) [4] A. Fard, B. Buckley, and B. Jalali, "Doubling the spectral efficiency of photonic time-stretch analog-to-digital converter by polarization multiplexing," Frontiers in Optics (2010) |
Silicon Photonics
 Empowering silicon with optical functions such as the ability to emit, guide, and modulate light could be the key to creating short-distance ultrafast optical interconnects that overcome one of the most formidable hurdles in scaling the speed of computing. An ultimate aim is the realization of silicon chips that communicate internally or with other chips using photons and optical waveguides and thus overcome the bandwidth limitations imposed by metallic interconnects. Yet another oppotunity lies in optical sensors with on-chip communication circuitry that can form nodes of intelligent sensor networks used for environmental and health monitoring. Guided by such visions and propelled by pioneering research conducted in the 1980s and 1990s, silicon photonics has enjoyed spectacular progress in the past several years. In 2004, we demonstrated lasing in silicon for the first time. For the past several years, we have developed various types of silicon-based photonic devices for next-generation optical communication and computing.
[1] B. Jalali, "Nonlinear optics in the mid-infrared," Nature Photonics 4, 506 (2010) [2] N. K. Hon, K. K. Tsia, D. R. Solli, and B. Jalali, "Periodically poled silicon," Applied Physics Letters 94, 091116 (2009) [3] K. K. Tsia, S. Fathpour, and B. Jalali, "Electrical tuning of silicon's dispersion," Applied Physics Letters 92, 061109 (2008) [4] B. Jalali, "Laser design: a cooler Raman laser," Nature Photonics 1, 691 (2007) [5] B. Jalali, "Teaching silicon new tricks," Nature Photonics 1, 193 (2007) [6] O. Boyraz and B. Jalali, "Demonstration of a silicon Raman laser," Optics Express 12, 5269 (2004) |
Physical Intelligence
 The Physical Intelligence (PI) program aspires to understand intelligence as a physical phenomenon and to make the first demonstration of the principle in electronic, photonics, and chemical systems. A central tenet is that intelligence spontaneously evolves as a consequence of thermodynamics in open systems. The PI program plan is organized around three interrelated task areas: (1) creating a theory and validating it in natural and engineered systems, (2) building the first human-engineered systems that display PI in the form of abiotic, self-organizing electronic, and chemical systems, and (3) developing analytical tools to support the design and understanding of PI systems. We are currently developing a photonics-based PI system.
[1] K. Drummond, "DARPA: Heat + Energy = Brains. Now make us some." Wired, May 8 (2009) [2] "Defense Sciences Office," DARPA (2010) |
Ultra-Wideband Time-Stretched Digitizer
 With increasing bandwidth demands from internet backbones, optical links with 100 Gb/s and higher data rates per wavelength channel are being targeted. To meet these demands, spectrally efficient modulation formats are being developed. The receivers in such links will require very high speed and resolution analog-to-digital converters (ADCs), which are currently beyond the capability of present day electronics. High-bandwidth digitizers are also needed for defense applications such as radars, and in detection of ultrafast electromagnetic pulses. In science, such digitizers are central tools in particle accelerators or X-ray free electron laser systems as well as in time-resolved fluorescence microscopy. The goal of this research is to use photonics to extend the capabilities of electronics to meet these demands. This is achieved by photonic time-stretch technology, which uses photonics to slow down electrical signals in time. Hence, an electronic digitizer that would have been too slow to capture the original electrical signal can now capture the stretched and slowed down signal. We have a world record for analog-to-digital conversion rate.
[1] S. Gupta and B. Jalali, "Time stretch enhanced recording oscilloscope," Applied Physics Letters 94, 041105 (2009) [2] J. Chou, O. Boyraz, D. R. Solli, and B. Jalali, "Femtosecond real-time single-shot digitizer," Applied Physics Letters 91, 161105 (2007) [3] Y. Han, O. Boyraz, and B. Jalali, "Tera-sample-per-second real-time waveform digitizer," Applied Physics Letters 87, 241116 (2005) [4] F. Coppinger, A. S. Bhushan, and B. Jalali, "Photonic time stretch and its application to analog-to-digital conversion," IEEE Transactions on Microwave Theory and Techniques 47, 1309 (1999) |
Generation and Control of Optical Rogue Waves
 Using real-time measurements, we have discovered a new phenomenon known as optical rogue waves, counterparts of the freak ocean waves thought to be responsible for destruction of ships on the open sea. Optical rogue waves arise in supercontinuum generation, a nonlinear process in which broadband radiation is generated from a narrowband light. By actively controlling the process behind the generation of rogue waves, we have shown that it is possible to produce a more stable and coherent white light source, which has the potential to impact many applications.
[1] D. R. Solli, C. Ropers, and B. Jalali, "Rare frustration of optical supercontinuum generation," Physical Review Letters 96, 151108 (2010) [2] B. Jalali, D. R. Solli, K. Goda, K. Tsia, and C. Ropers, "Real-time measurements, rare events, and photon economics," European Physical Journal Special Topics 185, 145 (2010) [3] D. R. Solli, C. Ropers, and B. Jalali, "Active control of rogue waves for stimulated supercontinuum generation," Physical Review Letters 101, 233902 (2008) [4] D. R. Solli, C. Ropers, P. Koonath, and B. Jalali, "Optical rogue waves," Nature 450, 1054 (2007) |
All-Dielectric Photonic-Assisted Radio Front-End Technology
 The threats to civil society posed by high-power electromagnetic weapons are viewed as a grim but real possibility in the world after September 11, 2001. These weapons produce a power surge capable of destroying or damaging sensitive circuitry in electronic systems. Unfortunately, the trend towards circuits with smaller sizes and voltages renders modern electronics highly susceptible to such damage. RF communication systems are particularly vulnerable, because the antenna provides a direct port of entry for electromagnetic radiation. To address this problem, we have proposed and demonstrated an all-dielectric photonic-assisted receiver. This RF receiver front-end features a complete absence of electronic circuitry and metal interconnects, the traditional 'soft spots' of a conventional RF receiver. The device exploits a dielectric resonator antenna to capture and deliver the RF signal onto an electro-optic field sensor. The dielectric approach has an added benefit in that it reduces the physical size of the front end, an important benefit in mobile applications.
[1] "Dielectric wireless receiver," Wikipedia [2] R. C. J. Hsu, A. Ayazi, B. Houshmand, and B. Jalali, "All-dielectric photonic-assisted radio front-end technology," Nature Photonics 1, 535 (2007) [3] A. Ayazi, R. C. J. Hsu, B. Houshmand, W. H. Steier, and B. Jalali, "All-dielectric photonic-assisted wireless receiver," Optics Express 16, 1742 (2007) |
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) |
Amplified Dispersive Fourier-Transform Spectroscopy
 In contrast to traditional spectroscopy in which an optical spectrum is obtained by spatially dispersing light with a prism or diffraction grating onto a detector array, we employ a new type of spectroscopy method known as amplified dispersive Fourier transformation - an optical process that maps the spectrum of an optical pulse into a time-domain waveform using group-velocity dispersion and simultaneously amplifies it in the optical domain. This technique removes spatial diffractive elements and a detector array in the conventional spectrometer and hence anables ultrafast real-time spectroscopic measurements at ~MHz scan rates. We are currently conducting real-time spectroscopic studies (e.g., Raman spectroscopy, absorption spectroscopy, etc.) of biological cells at ~MHz spectrum acquisition rates for next-generation cancer diagnostics and stem cell research.
[1] K. Goda and B. Jalali, "Noise figure of amplified dispersive Fourier transformation," Physical Review A 82, 033827 (2010) [2] K. Goda, D. R. Solli, K. K. Tsia, and B. Jalali, "Theory of amplified dispersive Fourier transformation," Physical Review A 80, 043821 (2009) [3] D. R. Solli, J. Chou, and B. Jalali, "Amplified wavelength-time transformation for real-time spectroscopy," Nature Photonics 2, 48 (2008) [4] K. Goda, D. R. Solli, and B. Jalali, "Real-time optical reflectometry enabled by amplified dispersive Fourier transformation," Applied Physics Letters 93, 031106 (2008) [5] J. Chou, D. R. Solli, and B. Jalali, "Real-time spectroscopy with subgigahertz resolution using amplified dispersive Fourier transformation," Applied Physics Letters 92, 111102 (2008) [6] J. Chou, Y. Han, and B. Jalali, "Time-wavelength spectroscopy for chemical sensing," IEEE Photonics Technology Letters 16, 1140 (2004) [7] P. V. Kelkar, F. Coppinger, A. S. Bhushan, and B. Jalali, "Time-domain optical sensing," Electronics Letters 35, 1661 (1999) |
Simultaneous Single-Fiber 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) |
Events & Seminars
IEEE Photonics LA Chapter
- Photonics Community in Los Angeles
Optical Society of So. Cal.
- Academic/Industry Networking
OSA/SPIE Student Chapter
- Activities and Networking for Students
Departmental Photonics Events
- Hosted by Electrical Engineering Dept.
Open Positions
Exciting projects are available for postdocs, graduate, and undergraduate students. Postdocs and students with fellowships will be given priority. Interested candidates should read this page and send a brief e-mail together with a CV to chaowang@ee.ucla.edu.