Integrated Photonics at Non-Telecom Wavelength

Optics Letters 44 (11), 2883-2886(2019)

The enthusiasm toward telecom-wavelength integrated photonics is primarily driven by the hope that silicon CMOS fabrication process can be leveraged to mass produce these components at an extremely low cost, as well as the potent to integrate with electronics. From the photon-matter interaction aspect, telecom-wavelength corresponds to the overtone of molecule folding and vibration. Thus, the corresponding absorption at the wavelength range is weak compared to visible, ultra-violet, and mid-infrared wavelength. In recent years, there is growing interest in integrated photonics at non-telecom wavelength range, such as mid-infrared and ultra-violet integrated photonics. Recently, we demonstrated on-chip Fourier Transform spectrometer centered at 3.4 um (left figure), and ultra-violet spectroscopy for protein quantitation.  

Integrated Photonics System

We build integrated photonic systems to address the problems and challenges that electronics could not solve on its own. For instance, the left figure shows an optical phased array chip for beam steering, which eliminates moving parts. As a result, it is not only more robust but also much faster than any mechanical beam steering solutions.  As the fabrication and integration method become mature, integrated photonics is becoming an intriguing approach for many applications. We are particularly interested in microwave photonics, analog photonics, optical computing, and ultra-short distance optical interconnect. 

Optics Letters 39 (4), 941-944(2014)

Highly Efficient Optoelectronic Devices

As the internet traffic continues to grow radically, the total power consumption for information processing, transportation, and storage will soon exceed the total electricity that can be produced. The importance of energy efficient devices can never be over emphasized. We focus on studying device physics and high performance materials such as polymers and BTO to reduce the power consumption. We have been able to reduce the power consumption of a ring modulator to 2.55 fJ/bit(left). The long term goal is to reach Atto-Joule per bit level, which represents the physics limit of electronic and photonic devices and will be the ultimate goal that can be achieved by nano-engineering. 

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Laser & Photonics Reviews 12, 1700300(2018)

We are developing highly sensitive on-chip photonic sensors for bio- and electromagnetic field sensing. We are continuously pushing the limit of the sensitivity by exploring novel photonic structures and materials. Leveraging slow light and slot waveguide, we have demonstrated an electromagnetic field sensors with 1.5 V/m sensitivity and remarkable bandwidth (left figure), which has been receiving intensive attention. Our recent demonstration of biosensors subwavelength metamaterials showed 0.1 ng/ml sensitivity, which can be used in disease screening, point-of-care applications, etc.  

On-Chip Photonic Sensors

Journal of Lightwave Technology 36, 1568-1575 (2018)

Because of the high index contrast, current silicon photonics based optical phased arrays cannot achieve small beam divergence and large field-of-view simultaneously without increasing fabrication complexity. To resolve the dilemma, we propose an ultra-long waveguide grating antenna formed by placing subwavelength segments within the evanescent field of a conventional strip waveguide. Bound state in the continuum effect is leveraged to suppress the sidewall emission. As a proof of concept, we theoretically demonstrated a millimeter-long through-etched waveguide grating antenna with a divergence angle of 0.081° and a feature size compatible with current silicon photonics foundries.

On-Chip optical phased array

Optics Express Vol. 29, Issue 10, pp. 15133-15144 (2021)