Using Quantum Photonics to Create Optical Frequency

combsTobias J. Kippenberg

The problem of the “whispering gallery”: observation of Lord Rayleigh in St. Paul Cathedral (London)**L. Rayleigh

Acoustic Whispering Gallery Mode

A photon storage time of 1 micro-second implies that the Light can travel up to 1 km inside a glass torus!

𝜏 h𝑃 𝑜𝑡𝑜𝑛>1𝜇𝑠𝑒𝑐𝑜𝑛𝑑

diameter of a human hair~100 µm

Coupling both to-and-from a 80m microtoroid on a chip

taper-microcavity junction exhibits extremely high ideality (coupling losses <0.3%)

Pin40 m

1/R

Coupling light into a microresonator

Just like a Guitar string has several vibrational modes, an optical microresonator has many optical modes

Silica Resonator (1)

Using Quantum Photonics to creat frequency combs

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At high intensities the interaction becomes nonlinear leading to «twin» photon generation

𝜔 𝐼=𝜔𝑝+ Δ𝜔𝑆=𝜔𝑝− Δ

PrismPump laser

Energy conservation requires

The Nobel Prize in Physics 1981Nicolaas BloembergenNonlinear Optics

Generating a frequency comb from a microresonator

Optical microresonator

Optical fiberPump laser

A frequency comb

Comb generation mechanism

Twin Photon generation

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Comb Generation Mechanism

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Twin photon generation

Der Entstehungsprozess: Zwillingphotonen

Twin photon generation

Generating a frequency comb in an optical microresonator

Optical frequency comb

𝜔𝑝+ Δ𝜔𝑝+2 Δ𝜔𝑝+3 Δ𝜔𝑝𝜔𝑝− Δ𝜔𝑝− 2 Δ𝜔𝑝− 3 Δ

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The perfectly equidistant arrangement is called on optical frequency comb

Δ Δ Δ ΔΔ

Microresonotor frequency comb

An octave spanning optical spectrum is generated from a single laser frequency

Optical frequency combs

Nobel Prize Physics 2005: “for their contributions to the development of laser-based precision spectroscopy, including the optical frequency comb technique"

HzWith an optical frequency combs an unknown optical frequency can be determined accurately measured

𝜔𝑜𝑝𝑡𝑖𝑞𝑢𝑒≈ 1015𝐻𝑧𝑇 𝑝𝑒𝑟𝑖𝑜𝑑≈ 10− 14 𝑠𝑒𝑐 .

Why are frequency combs interesting?

Frequency combs allow to create very accurate optical atomic clocks. Clocks that loose less than 1 second in the age of the universe of 14 Billion years…

Mode locked lasers for frequency comb generation

Ronald Holtzwarth, TWH

October 2005

T. Herr et al. Nature Photonics 2012 (July)

Frequency combs on a chip

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More than 1000 comb lines that are perfectly equidistant generated from a single laser…

Advantages of microresonator frequency combs

Vorteile:

- Very compact compact comb generator

- The distance between comb teeth is very large

Microresonator frequency combs as channel generators

Fiber optical communication uses several wavelength that travel down on optical fiber spaced in frequency by ca. >40 GHz

Applications of Frequency combs in Telecommunication

Today: picture of 4 laser modules to generate 4 channels…

Future: A single microresonator can generate > 1000 channels from a single laser

Astrophysical spectrometer: searches for exoplanets

Microresonator frequency combs can assist to calibrate astrophysical spectrometers

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First spectrometer calibration with a Microcavity

ESO‘s Very Large Telescope (VLT) in Chile X-Shooter spectrometer (in Munich)

Microcavity comb spectrum (83 GHz mode spacing) on echelle grating based spectrometer

Frequency comb assisted spectrometer calibration

X-Shooter Telescope (ESO)

Microresonator frequency combs…

Applying them in astrophysical planets searches as calibratoin tool..

…applying them in space optical clocks…

… enable them to become sources of mid IR radiation used in chemistry or pharmaceutical minitoring..

.. Linking RF to optical on a chip…