Bahl Research Group
Lithium niobate optical isolators on-chip.
D.B. Sohn, O.E. Orsel, G. Bahl, "Electrically driven linear optical isolation through phonon mediated Autler-Townes splitting," arXiv:2104.04803, 2021. [arXiv preprint]
Acoustically-pumped optical isolators on an aluminum nitride chip.
D.B. Sohn, S. Kim, G. Bahl, "Time-reversal symmetry breaking with acoustic pumping of nanophotonic circuits", Nature Photonics, doi:10.1038/s41566-017-0075-2, Feb 2018. [Nature link]
Exploring chiral physics in ultra-high Q whispering gallery resonators.
S. Kim, X. Xu, J.M. Taylor, G. Bahl, "Dynamically induced robust phonon transport and chiral cooling in an optomechanical system", Nature Communications 8, 205, doi:10.1038/s41467-017-00247-7, 2017. [Nature link]
Microwave implementation of quadrupole topological insulator.
C.W. Peterson, W.A. Benalcazar, T.L. Hughes, G. Bahl, "Demonstration of a quantized microwave quadrupole insulator with topologically protected corner states," Nature, 555, pp.346-350, doi:10.1038/nature25777, 2018 [Nature link]
Photograph of fluid meniscus in an ultrahigh-Q opto-mechano-fluidic resonator (OMFR).
K. Han, J. Kim, G. Bahl, "High-Throughput Sensing of Freely Flowing Particles with OptoMechanoFluidics", Optica, vol.3, no.6, pp. 585-591, 2016. [Optica link]
Artist visualization of Raman Cooling of a silicon photonic crystal.
Y. Chen, G. Bahl, "Raman Cooling of Solids through Photonic Density of States Engineering," Optica, 2(10), p.893-899, 2015. [Optica link]
Visualization of slow, fast, and stopped light in Brillouin Scattering Induced Transparency.
J. Kim, M. Kuzyk, K. Han, H. Wang, G. Bahl, "Non-reciprocal Brillouin scattering induced transparency," Nature Physics, 11, pp. 275-280, doi:10.1038/nphys3236, 2015. [Nature link]

Gaurav Bahl
[Curriculum Vitae]
4413 Mechanical Engineering Laboratory,
105 S. Matthews
Urbana, IL 61801

Tel: (217) 300-2194

Research Overview

The Bahl Research Group performs experimental research at the interface between optical and mechanical systems. Of particular interest are the mechanisms by which light interacts mechanically with photonic microdevices (i.e. via radiation pressure, gradient force, electrostrictive pressure, and photothermal effects), and how mechanical devices can affect and manipulate light.

See Research for more details.


Postdoc openings: MEMS-based clocks and integrated photonics.

RA openings in MEMS, photonics, and RF circuits for quantum applications.

We are always on the lookout for graduate and undergraduate researchers with background in the following topics -- electromagnetics, photonics, microfabrication, material physics, nonlinear optics, MEMS and NEMS, and circuit design. Experimental experience is strongly preferred. Interested students must already be admitted to UIUC and should contact Prof. Bahl with a complete CV highlighting relevant experience.

Latest News

18 Oct 2023
Congratulations to Dr. Ogulcan Orsel on defending his thesis!

18 Sept 2023
Our paper on demonstration of non-reciprocal polarization rotation, without any magneto-optical effect, has been published in APL Photonics. This new electro-optic effect was seen to outperform magneto-optic materials by 10-50x on the key figure of merit! Congratulations to Ogulcan on a great result!

25 May 2023
The Chicago Quantum Exchange has written a nice feature on our experimental work demonstrating a quadrupole photonic topological insulator using orbital induced synthetic flux. This was a great collaboration with our Kaiserlautern friends. Original article at Nature Communications.

8 May 2023
Our experimental work on rank-2 chirality is featured on EurekAlert.

9 Feb 2023
Congratulations to Penghao for publishing the first realization of rank-2 non-Hermitian skin effect in Nature communications!

1 Dec 2022
Our work on record setting chip-scale optical isolators was selected as a top-30 development in optics for 2022! Read the summary on lithium niobate optical isolators that outperform magneto-optics and check out the entire Optics in 2022 feature article here.

8 Nov 2022
Gaurav has been elected into the 2023 Class of Optica Fellows!

3 Nov 2022
Jiho and our collaborators from Kaiserlautern (Germany) have published a fantastic new demonstration of a high-order topological insulator that leverages higher orbitals. Check out the paper in Nature Communications.

15 Aug 2022
Gaurav was promoted to Full Professor at UIUC.

19 Apr 2022
Sasha and Tianhe demonstrated that an incomplete dislocation defect in a crystal can produce a new kind of trapped state in a topological material. This technically challenging study was published in Nature Communications.

28 Dec 2021
Rhinithaa's paper on magneto-mechanical transmitters that can send signals through earth and through seawater appears in IEEE Transactions on Antennas and Propagation. Great work by a fantastic team of coauthors!

20 Oct 2021
We have developed a record breaking ultralow-loss optical isolator on-chip, using a lithium niobate platform. Our paper has appeared in Nature Photonics and was also selected for the hero image! The Illinois Quantum Information Science and Technology Center (IQUIST) has prepared a wonderful press release on this work. Congratulations to Benjamin and Ogulcan!

15 July 2021
Our commentary in Nature Photonics explores a new study that emulates some of the most exciting physics of PT symmetry and exceptional points using only basic components.

29 Apr 2021
Congratulations to Jeewon Suh on a successful PhD thesis defense!

20 Jan 2021
Kitt and Tianhe's new paper demonstrates the trapping of topological modes and fractional charges at disclination defects (rotational defects) in high-order topological insulators. The paper has appeared in Nature! The Illinois Quantum Information Science and Technology Center (IQUIST) has prepared a press release on this work.

04 Jan 2021
Soonwook's new paper in APL Photonics demonstrates nonreciprocity through a synthetic Hall effect for light. The paper was also selected as an Editor's Pick at the journal.

14 Dec 2020
Inbar's new paper in Phys. Rev. Applied demonstrates that lattice dislocations can produce localized modes in weak topological insulators. The experiments were done using magneto-mechanical resonator arrays.

17 July 2020
Kitt's PhD work was featured in an article from MechSE.

1 July 2020
Gaurav is now a Senior Member of the Optical Society of America!

16 Jun 2020
Congratulations to Kitt Peterson on a successful PhD thesis defense!

5 Jun 2020
Kitt and Tianhe's paper on using a fractional corner anomaly to identify high order topological insulators appears in Science! The College of Engineering has prepared a press release on this work.

17 Apr 2020
Congratulations to Benjamin Sohn on a successful PhD thesis defense!

9 Mar 2020
Congratulations to Jeewon Suh for being selected as an "outstanding TA" for the MechSE department for Fall 2019!

26 Feb 2020
Our team was selected to receive a MURI grant on Robust Photonic Materials with High-Order Topological Protection. Excited to be working with Mikael Rechtsman, Taylor Hughes, Bo Zhen, Marin Soljacic, Mohammad Hafezi, Wladimir Benalcazar, and other great athletes!

21 Feb 2020
Inbar's paper on topologically robust temporal pumping has appeared in Nature Communications.

21 Aug 2019
OSA's Optics and Photonics News covered our work on suppressing Rayleigh backscattering in microresonators.

19 Aug 2019
Our review paper on Brillouin Integrated Photonics appears in Nature Photonics. Great coverage from Popular Mechanics and the University of Sydney.

12 July 2019
Seunghwi's paper on dynamic suppression of Rayleigh scattering in microresonators is accepted for publication at Optica.

10 July 2019
Kitt's paper on Strong nonreciprocity in modulated resonator chains through synthetic electric and magnetic fields is accepted for publication at Physical Review Letters.

2 July 2019
Gaurav is a recipient of the Presidential Early Career Award for Scientists and Engineers (PECASE)! Link to article by the Illinois News Bureau.

27 April 2019
Inbar's paper on the magnetostatic spring effect was published in IEEE Transactions on Magnetics.

1 Dec 2018
Each year, the December issue of Optics & Photonics News - the monthly magazine of The Optical Society - highlights the most exciting optics research to emerge in the preceding 12 months. Our work on "Breaking Optical Symmetry with Sound" was selected this year for Optics in 2018!

5 Nov 2018
PhD season wraps up with JunHwan successfully defending his thesis!

30 Oct 2018
Yinchung successfully defends his thesis! Second of three.

24 Oct 2018
PhD season begins with Seunghwi successfully defending his thesis!

16 Aug 2018
Gaurav is formally promoted to Associate Professor with tenure.

8 June 2018
Kitt and Seunghwi's paper on nonreciprocal coupling appears in Science Advances.

12 Apr 2018
Kitt is selected as a Mavis Future Faculty Fellow for 2018-2019.

16 Mar 2018
Seunghwi was recognized as a Distinguished Graduate Student in 2017 by MechSE. Congratulations!

15 Mar 2018
Our paper on the demonstration of a quadrupole topological insulator has appeared in Nature. Feature articles on this work appeared in Gizmodo and by the Illinois News Bureau.

2 Feb 2018
Gaurav is awarded a 2018 Dean's Award for Excellence in Research.

22 Jan 2018
Benjamin's paper on breaking time-reversal symmetry with sound waves appears in Nature Photonics and is featured as the Feb 2018 journal cover! Articles on the work were written by the UIUC News Bureau, and in Nature Photonics News & Views.

12 Oct 2017
We are now developing mechanical transmitter technologies as part of a multi-group collaboration funded by DARPA.

7 Aug 2017
Seunghwi's paper on chiral optomechanical cooling and disorder suppression appears in Nature Communications. The work is also featured by the UIUC College of Engineering.

24 July 2017
Congratulations to Dr. Inbar Grinberg on winning postdoctoral fellowships from both the Zuckerman STEM Leadership Program and the Israel council for higher education.

12 May 2017
Congratulations to Kewen on winning a 2017 Chinese Government Award for outstanding students studying abroad.

8 May 2017
Congratulations to JunHwan and Seunghwi on getting their paper on achieving complete optical isolation published in Scientific Reports! The work was also featured by the College of Engineering.

24 Apr 2017
The College of Engineering recognizes numerous young faculty awards netted by our faculty.

16 Feb 2017
Congratulations to (nearly Dr.) Kewen Han on passing his PhD defense!

7 Feb 2017
Gaurav has won a ONR Director for Research Early Career grant ($1M) to pursue experimental research on reconfigurable microwave and acoustic nonreciprocal systems.

13 Jan 2017
Seunghwi's paper on dual optical densities of states on Brillouin cooling appears in Optics Express. The work demonstrates operation close to strong coupling and saturation of Brillouin cooling.

21 Dec 2016
Jeewon's paper in APL Photonics presents the fastest fly-by optomechanical particle sensor to date, capable of speeds exceeding 30,000 particles/second.

29 Nov 2016
Yinchung and Seunghwi reveal the regimes of operation of Brillouin cooling in linear waveguides in the New Journal of Physics.

17 Sept 2016
The work of our EFRI teammate (Prof. Steven Cummer, Duke) is featured as part of the National Science Foundation #waveweek series.

15 Aug 2016
Our team has won a major research grant to explore New Light and Acoustic Wave Propagation (NewLAW), funded through the NSF Emerging Frontiers in Research and Innovation (EFRI) program. This 4-year research project will be conducted in close collaboration with our co-PIs Prof. Taylor Hughes (UIUC Physics), Prof. Steve Cummer (Duke ECE), and Prof. Hailin Wang (Oregon Physics). Article from Engineering@Illinois

22 June 2016
Our opto-mechano-fluidics research is featured on the cover of the June 2016 edition of Optica.

1 June 2016
Our paper on High-Throughput Sensing of Freely Flowing Particles with OptoMechanoFluidics is published in Optica!

21 May 2016
Kitt Peterson's fantastic outreach efforts with middle-school children are featured in I-STEM and MechSE Today. Kitt taught students how to design and 3D print their own keychains!

29 March 2016
Congratulations to Christopher Peterson for winning a National Science Foundation Graduate Research Fellowship for 2016.
Our group continues to maintain its 100% success rate on this program with three fellowship recipients till date!

8 March 2016
Our group has won a DURIP award from AFOSR to build a telecom wavelength Raman spectrometer!

4 March 2016
Congratulations to Kewen for winning a 2016 Yee Fellowship from the College of Engineering!

19 Februrary 2016
Congratulations to Kewen for being honored by MechSE as a Distinguished Graduate Student for 2015!

29 January 2016
Congratulations to Seunghwi and Yin-Chung on passing their qualifying exams!

23 September 2015
Multiple updates! -- Nathan and Seunghwi's paper on Giant Gain Enhancement in Surface-Confined Resonant Stimulated Brillouin Scattering is accepted for publication in Laser & Photonics Reviews. Gaurav's chapter on Microfluidic Optomechanics for the 2015 edition of the Encyclopedia of Nanotechnology is also accepted. Gaurav celebrates 5 years since receiving his PhD.

15 September 2015
Our paper on Raman Cooling of Solids through Photonic Density of States Engineering is accepted for publication in Optica.

15 April 2015
Congratulations to Jafir for winning an undergraduate research grant from the MechSE Society of Engineering Mechanics.

31 March 2015
Benjamin Sohn was awarded a National Science Foundation Graduate Research Fellowship. Congratulations on this fantastic achievement!

26 January 2015
Non-Reciprocal Brillouin Scattering Induced Transparency appears in Nature Physics.
Congratulations to the team and to our collaborators from Oregon.
Associated news story here.

20 January 2015
Gaurav wins the AFOSR Young Investigator Award (YIP) for proposed work on Chip-Scale Linear Non-Reciprocal Optomechanical Systems. Several major victories for Illinois Engineering.

2 December 2014
Benjamin's outreach efforts with students at the Dr. Howard Elementary School in Champaign are featured on I-STEM.

15 October 2014
Gaurav Bahl, Benjamin Sohn, Shengtai Shi, and Joseph Muskin spent the week at University of Illinois Laboratory High School working with Sharlene Denos and her class on resonant optomechanical sensors.

26 August 2014
It's been a good summer with papers in Journal of Visualized Experiments, Applied Physics Letters, European Physical Journal, and Scientific Reports! Good work team!

1 April 2014
Congratulations to Nathan for winning the NSF Graduate Research Fellowship!

14 Jan 2014
Congratulations to Kewen and JunHwan for their Optics Express paper on multimode aerostatically tunable optomechanical oscillators.

2 December 2013
Nathan's educational activities with 4th graders at Stratton Elementary school are featured in the MechSE weekly news and on the I-STEM website.

26 November 2013
Optics in 2013: "Bridging two worlds: Microfluidic optomechanics" appears in OPN Magazine December 2013 issue (pg. 39). This issue of the monthly magazine of The Optical Society highlights the most exciting optics research to emerge in the preceding 12 months.

11 November 2013
"Cavity optomechanics on a microfluidic resonator with water and viscous liquids" appears in Light Science & Applications .

15 October 2013
Kyu Hyun Kim's paper on Microfluidic Optomechanics is a winner of the Emil Wolf Outstanding Student Paper Competition at Frontiers in Optics 2013.

7 October 2013
Optics in 2013! Each year, the December issue of Optics & Photonics News - the monthly magazine of The Optical Society - highlights the most exciting optics research to emerge in the preceding 12 months. Our submission on Microfluidic Optomechanics has been selected this year!

8 July 2013
Kewen's first conference paper on multi-mode optomechanical pressure sensing is accepted to Frontiers in Optics 2013. Congratulations!

7 Jun 2013
"Brillouin cavity optomechanics with microfluidic devices" appears in Nature Communications. The work is featured on,, and UIUC College of Engineering.

29 Apr 2013
Our research on Brillouin cooling is highlighted in Nature Photonics, Vol. 7, 348-349 (2013) in article titled View from... 2013 Photonics West: Solid cooling.

1 Dec 2012
Our work on Brillouin cooling is featured in the OSA Optics and Photonics News "Optics in 2012" issue which highlights the most exciting optics research to have emerged in the past 12 months.

7 Aug 2012
New course offered: ME498-PM4 Photonic MEMS. Read more.

19 Apr 2012
Gaurav will start as MechSE faculty at UIUC in Fall 2012!

22 Jan 2012
"Observation of spontaneous Brillouin cooling" appears in Nature Physics.

22 Jan 2012
Our work on Brillouin cooling is featured in Nature Physics News & Views!

List of Publications

Click here for Publications page.