Case Study CS-LDTC07 Rev. A

Page 5

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KEYWORDS

Quantum Cascade Laser, Frequency Comb, Room

Temperature, Terahertz, Harmonic, Distributed-feedback

Grating, Mid-IR, Multiheterodyne Spectroscopy

PRODUCT USED

QCL2000 LAB, PTC10K-CH, TC5 LAB

REVISION HISTORY

Document Number: CS-LDTC07

REVISION

DATE

NOTES

A

June 2020

Initial Release

REFERENCES

1. Lu, Q., Wang, F., Wu, D. et al. Room temperature

terahertz semiconductor frequency comb. Nat Commun

10, 2403 (2019). doi.org/10.1038/s41467-019-10395-7

2. Kazakov, D. et al. Self-starting harmonic frequency

comb generation in a quantum cascade laser. Nat.

Photonics

11, 789–792 (2017).

doi.org/10.1038/s41566-017-0026-y

3. Paschotta, R. Frequency Combs. RP-Photonics.com.

https://www.rp-photonics.com/frequency_combs.html

4. Piccardo, M. et al. Radio frequency transmitter based

on a laser frequency comb. Proc. Natl Acad. Sci. USA

116, 9181 (2019). doi.org/10.1073/pnas.1903534116

USEFUL LINK

•

QCL2000 LAB Product Page

•

PTC10K-CH Product Page

•

TC5 LAB Product Page

OPEN ACCESS

The figures and data used for this case study were obtained

from Reference 1. The article (Ref. 1) is distributed under

terms of Creative Commons Attribution 4.0 International

License

(https://creativecommons.org/licenses/by/4.0/),

which permits unrestricted use, distribution, and

reproduction in any medium, provided that you give

appropriate credit to the original authors and the source,

provide a link to the Creative Commons license, and

indicate if changes were made.

Figures 2 and 4 were cropped or the format was changed.

No changes were made to the other images. They are

presented here in their original form.

The captions for Figures 2 and 4 have been modified from

their original form.

WAVELENGTH'S ROLE

The QCLs operation state is highly dependent on the

injection current. Because the harmonic comb state is

accomplished with slightly more current than single-mode

state, it is crucial that the QCLs are properly and accurately

driven and have stable temperature control.

Wavelength Electronics' QCL2000 LAB QCL drivers

(

Figure 6 left) provide up to 2.0 A of current to the QCLs

with noise current as low as 0.4 µA (RMS). The average

noise density of 4 nA/√Hz is necessary for the design of the

room temperature frequency comb. These high-precision

and ultra-low noise current sources provide the necessary

stability for harmonic frequency combs.

Wavelength Electronics' PTC10K-CH temperature controller

(

Figure 6 right) provides up to ±10 A of current to the TEC

to stabilize the temperature of the QCLs. The PTC has

temperature stability of less than 0.0012ºC which surpasses

the required temperature stability of less than 10 mK in the

experiment. The compact and accurate design of the PTC

enables total temperature control of the lasers.

At Harvard University, both studies use Wavelength

Electronics' TC5 LAB (

Figure 6 top) to control the

temperature of the QCLs. The TC5 LAB has temperature

stability as precise as 0.0002ºC which also surpasses the

precision of better than 10 mK required. QCL2000 LABs are

also used to drive the QCLs at the varying current levels

with the same noise levels listed for the Northwestern

University study.

Figure 6. Wavelength Electronics' TC5 LAB (top),

QCL2000 (left), and PTC10K-CH (right)