Red Lasers

Definition: lasers emitting red light

German: rote Laser

Category: laser devices and laser physics

Cite the article using its DOI: https://doi.org/10.61835/opr

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This article deals with lasers emitting in the red spectral region, i.e. with a wavelength roughly around 625–700 nm. The following types of red lasers are the most common:

Red laser diodes, based on, e.g., GaInP or AlGaInP quantum wells, are available with different output power levels, ranging from a few milliwatts (single emitters, VCSELs) to the order of 100 W from diode bars. Typical wavelengths are 635, 650 and 670 nm. The shorter wavelengths have significantly better visibility for the human eye, but are more difficult to generate efficiently. Red laser diodes are often used for laser pointers.
Various gas lasers can emit red light. In particular, helium–neon lasers are suitable for smaller powers at 632.8 nm, whereas krypton lasers can generate high powers at 647.1 nm.
Lasers based on praseodymium-doped (and sometimes ytterbium-codoped) ZBLAN fibers can emit around 635 nm. Hundreds of milliwatts of output power and very high beam quality are achievable. One may use a blue laser for pumping, but it is also possible to realize upconversion lasing with infrared pumping.
Red bulk lasers can be based on, e.g., laser crystals of ruby (chromium-doped sapphire, Cr³⁺:Al₂O₃), and also on Pr³⁺:YLF and Pr³⁺:LiLuF₄ [8]. Titanium–sapphire lasers emit mostly in the infrared region, but can be tuned down to roughly 650 nm.
There are various types of frequency-doubled lasers, where the actual laser emits in the 1.2–1.3-μm spectral region and a frequency doubler converts this radiation into red light. For example, 660-nm light can be generated with frequency-doubled Nd:YAG lasers, 656.5 nm with Nd:YLF, or 671 nm with Nd:YVO₄ or Nd:GdVO₄. Output powers of multiple watts can be obtained with high beam quality.
Some red laser sources are based on other nonlinear frequency conversion devices, involving e.g. sum frequency generation or parametric oscillation. For example, an OPO with intracavity sum frequency generation can generate red light [3].
There are optically pumped semiconductor lasers (VECSELs) which can either directly emit red light [5], or generate red light via intracavity second-harmonic generation [7].

Light from lasers operating at somewhat longer wavelengths, such as 750 or even 800 nm, can still be perceived as red light, if it is sufficiently intense. (There is no sharp boundary between the visible and the infrared spectral regions.) It can, however, be hazardous to view such light because such intensity levels required for good visibility can damage the retina.

Applications of Red Lasers

Red lasers are applied e.g. as laser pointers, for bar scanners and other laser scanners, for optical data recording or retrieval (e.g. on DVDs), for laser projection displays, for interferometers, for pumping of certain solid-state lasers (e.g. Cr:LiSAF or Cr:LiCAF), and in medical therapies (e.g. photodynamic therapy).

Suppliers

The RP Photonics Buyer's Guide contains 87 suppliers for red lasers. Among them:

TOPTICA Photonics

TOPTICA offers a large variety of wavelength-selected single-mode laser diodes. Among more standard laser diodes you will also find "rarities", i.e. diodes with output wavelengths that only TOPTICA provides. The diodes can be purchased separately. In addition TOPTICA can integrate any diode from the stock lists into a tunable diode laser system: Fabry–Perot or AR-coated laser diodes may be integrated into a diode laser systems, DFB/DBR laser diodes into a DFB pro and Tapered Amplifier into an TA system.

Each type of diode is carefully tested in an external cavity laser configuration with respect to coarse tuning range, mode-hop-free tuning range and power limits. The results are disclosed on request to the customer in a detailed datasheet. In case you can still not match your wavelength of choice, contact TOPTICA – and chances are very high that we can provide it within very short time.

MPB Communications

Red fiber lasers were the earliest models developed for the cutting-edge microscopy platforms built in the laboratories of Dr. Stefan Hell, and flow cytometry platforms tested in the lab of Dr. William Telford of the Core Flow Cytometry Facility at N.I.H. where beam quality, reliability, and stability continue to be of the utmost importance.

Wavelengths from 620 nm to 775 nm are available in either an OEM compact package, and/or a 2RU rack mountable package with integrated power supply and are equiped with a user-friendly graphical user interface for ease of setup and operation. MPB offers an optional fiber coupling service which provides the user up to 1 watt out of the fiber.

Applications where MPBC red lasers are used include microscopy, genomics, optogenetics, DNA/RNA sequencing etc.

Bibliography

[1]	H. B. Seereze and C. M. Harding, “100 W 671 nm visible laser diode array”, Electron. Lett. 28 (23), 2115 (1992); https://doi.org/10.1049/el:19921357
[2]	B. Lu et al., “400 mW continuous-wave diffraction limited flared unstable resonator laser diode at 635 nm”, Electron. Lett. 33, 1633 (1997); https://doi.org/10.1049/el:19971115
[3]	W. R. Bosenberg et al., “2.5-W, continuous-wave, 629-nm solid-state laser source”, Opt. Lett. 23 (3), 207 (1998); https://doi.org/10.1364/OL.23.000207
[4]	Sun et al., “Generation of 11.5 W coherent red-light by intra-cavity frequency-doubling of a side-pumped Nd:YAG laser in a 4-cm LBO”, Opt. Commun. 241, 167 (2004); https://doi.org/10.1016/j.optcom.2004.06.063
[5]	J. E. Hastie et al., “High power CW red VECSEL with linearly polarized TEM₀₀ output”, Opt. Express 13 (1), 77 (2004); https://doi.org/10.1364/OPEX.13.000077
[6]	C. Du et al., “6-W diode-end-pumped Nd:GdVO₄/LBO quasi-continuous-wave red laser at 671 nm”, Opt. Express 13 (6), 2013 (2005); https://doi.org/10.1364/OPEX.13.002013
[7]	A. Härkönen et al., “High power frequency doubled GaInNAs semiconductor disk laser emitting at 615 nm”, Opt. Express 15 (6), 3224 (2007); https://doi.org/10.1364/OE.15.003224
[8]	A. Richter et al., “Power scaling of semiconductor laser pumped praseodymium-lasers”, Opt. Express 15 (8), 5172 (2007); https://doi.org/10.1364/OE.15.005172
[9]	P. Adamiec et al., “Tapered lasers emitting at 650 nm with 1 W output power with nearly diffraction-limited beam quality”, Opt. Lett. 34 (16), 2456 (2009); https://doi.org/10.1364/OL.34.002456

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