Microresonators offer a simpler approach to sensing with light pulses

October 01, 2018

Ultrashort optical pulses are becoming more and more relevant in a number of applications including distance measurement, molecular fingerprinting and ultrafast sampling. Many of these applications rely not only on a single stream of pulses - also known as "optical frequency combs" - but require two or even three of them. Nonetheless, these multi-comb approaches significantly speed up acquisition time over conventional techniques.

These trains of short optical pulses are typically produced by large pulsed laser sources. Multi-comb applications therefore require several such lasers, often at prohibitive costs and complexity. Furthermore, the relative timing of pulse trains and their phases must be very well synchronized, which requires active electronics that synchronize the lasers.

In a new paper published in Nature Photonics, the research team of Tobias J. Kippenberg at EPFL, together with the group of Michael Gorodetsky at the Russian Quantum Centre, has developed a much simpler method to generate multiple frequency combs. The technology uses small devices called "optical microresonators" to create optical frequency combs instead of conventional pulsed lasers.

The microresonator consists of a crystalline disk of a few millimeters in diameter. The disk traps a continuous laser light and converts it into ultrashort pulses - solitons - thanks to the special nonlinear properties of the device. The solitons travel around the microresonator 12 billion times per second. At every round, a part of the soliton exits the resonator, producing a stream of optical pulses.

The microresonator the researchers used here has a special property in that it allows the light to travel in the disk in multiple different ways, called spatial modes of the resonator. By launching continuous lightwaves in several modes at the same time, multiple different soliton states can be obtained simultaneously. In this way, the scientists were able to generate up to three frequency combs at the same time.

The working principle is the same as spatial multiplexing used in optical fiber communication: the information can be sent in parallel on different spatial modes of a multimode fiber. Here, the combs are generated in distinct spatial modes of the microresonator.

The method has several advantages, but the primary one is that it does not require complex synchronization electronics. "All the pulses are circulating in the same physical object, which reduces potential timing drift, as encountered with two independent pulsed lasers," explains Erwan Lucas, first author of the paper. "We also derive all the continuous waves from the same initial laser by using a modulator, which removes the need for phase synchronization."

Using this multiplexing scheme, the team demonstrated several applications, such as dual-comb spectroscopy, or rapid optical sampling. The acquisition time could be adjusted between a fraction of a millisecond to 100 nanoseconds.

The authors are now working on developing a new demonstration with the triple-comb source: "We had not planned for a demonstration, as we did not expect our scheme to work so easily," says Lucas. "We are obviously working on it."

The technology can be integrated with both photonic elements and silicon microchips. Establishing multi-comb generation on a chip may catalyze a wide variety of applications such as integrated spectrometers or LIDAR, and could make optical sensing far more accessible.
-end-
Reference

E. Lucas, G. Lihachev, R. Bouchand, N. G. Pavlov, A. S. Raja, M. Karpov, M. L. Gorodetsky, T. J. Kippenberg. Spatial multiplexing of soliton microcombs. Nature Photonics 01 October 2018. DOI: 10.1038/s41566-018-0256-7

Ecole Polytechnique Fédérale de Lausanne

Related Light Articles from Brightsurf:

Light from rare earth: new opportunities for organic light-emitting diodes
Efficient and stable blue OLED is still a challenge due to the lack of emitter simultaneously with high efficiency and short excited-state lifetime.

Guiding light: Skoltech technology puts a light-painting drone at your fingertips
Skoltech researchers have designed and developed an interface that allows a user to direct a small drone to light-paint patterns or letters through hand gestures.

Painting with light: Novel nanopillars precisely control intensity of transmitted light
By shining white light on a glass slide stippled with millions of tiny titanium dioxide pillars, researchers at the National Institute of Standards and Technology (NIST) and their collaborators have reproduced with astonishing fidelity the luminous hues and subtle shadings of 'Girl With a Pearl Earring.'

Seeing the light: Researchers combine technologies for better light control
A new technology that can allow for better light control without requiring large, difficult-to-integrate materials and structures has been developed by Penn State researchers.

A different slant of light
Giant clams manipulate light to assist their symbiotic partner.

New light for plants
Scientists from ITMO in collaboration with their colleagues from Tomsk Polytechnic University came up with an idea to create light sources from ceramics with the addition of chrome: the light from such lamps offers not just red but also infrared (IR) light, which is expected to have a positive effect on plants' growth.

Scientists use light to accelerate supercurrents, access forbidden light, quantum world
Iowa State's Jigang Wang continues to explore using light waves to accelerate supercurrents to access the unique and potentially useful properties of the quantum world.

The power of light
As COVID-19 continues to ravage global populations, the world is singularly focused on finding ways to battle the novel coronavirus.

Seeing the light: MSU research finds new way novae light up the sky
An international team of astronomers from 40 institutes across 17 countries found that shocks cause most the brightness in novae.

Seeing the light: Astronomers find new way novae light up the sky
An international team of researchers, in a paper published today in Nature Astronomy, highlights a new way novae light up the sky: this is shocks from explosions that create the novae that cause most of the their brightness.

Read More: Light News and Light Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.