Optoelectronics Company LOGO
Ushio HL67203HD and HL69203HD laser diodes

The Best Deep Red Laser Diode Wavelengths (670~690nm) for Biomedical Applications

RELEASE: March 2022

There are many applications for red laser diodes and the wavelengths selected for each application must be suitable for the purpose of the application and the characteristics of the wavelength itself. This article focuses mainly on the biomedical applications of deep red laser diodes (670–690nm).


Applications of Red Laser Diodes at Various Wavelengths


640nm Wavelength

The 640nm band is used in line lasers and laser pointers for positioning and levelling. This wavelength has very high visibility so the laser light appears brighter to the eyes. For applications such as laser TVs and laser projectors, where images are created by mixing colours of RGB lasers, 640nm is a widely used wavelength as it has both high visibility and a wide colour range.

Before the commercialisation of laser diodes, helium-neon (He-Ne) lasers (632.8nm) were widely used for fluorescence excitation and scattering measurements as a stable light source. Nowadays, laser diodes in the 640nm band, which is close to the He-Ne laser wavelength, are used for fluorescence bio-imaging, e.g. confocal microscopy and scattering measurements such as flow cytometry and particle size measurement.

660nm Wavelength

Lasers for recording and reading DVDs were standardised at a wavelength of 660nm and the performance of the lasers has improved as the market has grown. Laser diodes of this wavelength have been adopted for many applications such as industrial line lasers and measurement lasers.

670nm-690nm Wavelength

Light in the 670~690nm band, which is slightly longer, is characterised by a particularly deep penetration depth into biological tissues among red light, which is about 2–3 mm in the case of human skin. Along with this, the existence of photosensitisers (porphyrin compound) that are highly bio-compatible, absorb red light and generate reactive oxygen species has led to the application of light as a method of therapeutic treatment.


Deep red laser skin penetration


Therapy using Light: Photodynamic-therapy and Photo-immunotherapy


Photodynamic-therapy (PDT) is a treatment method in which a photosensitiser with a high affinity for the lesion is administered and then light is irradiated to selectively destroy only the lesion tissue by reactive oxygen species generated in the tissue. PDT is used in the treatment of lung cancer, oesophageal cancer, malignant brain tumours, and age-related macular degeneration. Typical photosensitisers are porphyrin compounds such as Talaporfin sodium (peak absorption wavelength: 664nm, marketed as Laserphyrin®) and Verteporfin (peak absorption wavelength: 689nm, marketed as Visudyne®)2). For PDT, lasers are widely used because they are easy to guide through optical fibres and provide the necessary illumination. Laser diodes, which have recently become capable of producing high output power in Watt class, are also widely used.


Therapy using Light: Photodynamic-therapy and Photo-immunotherapy


Photo-immunotherapy (PIT), a completely new method of cancer treatment using light, is also gaining attention. PIT involves the administration of antibodies conjugated with photosensitive phthalocyanine compound (IR700), and then light irradiation. The peak absorption wavelength of IR700 is around 690nm and, like PDT, laser diodes are often used.


Therapy using Light: Photodynamic-therapy and Photo-immunotherapy


Recommended laser diodes for biomedical applications


The latest Ushio 670-690nm biomedical laser diode product line-up

Above are some examples of Ushio laser diodes with lasing wavelengths in the 670–690nm region that are suitable for the biomedical applications described in this article:

The Ushio HL67001DG and HL69001DG are laser diodes with lasing wavelengths of 675nm or 690nm and optical output power of 200 mW (CW), the highest level for a single-mode laser diode in this wavelength region. The HL67001DG & HL69001DG are both suitable for a wide range of applications in the biomedical field including the development of photosensitisers. They both feature a compact TO-CAN package of 5.6 mm in diameter with a built-in photodiode to monitor the optical output power in the CAN package for easy optical output control.

Two new laser diodes: HL67203HD and HL69203HD, also with lasing wavelengths of 675nm or 690nm, are multi-mode laser diodes with high output power of 1.2 W (CW), and feature extremely high optical output efficacy (WPE) of 40% and 41%, respectively. The HL67203HD & HL69203HD are both suitable for PDT, PIT and other applications requiring high output power.

All the above four laser diodes can be driven in a temperature range of -10 to 75°C, making them suitable for integration into light source equipment.

In addition to the laser diodes introduced here, the Optoelectronics Company offers a wide range of Ushio laser diodes to meet your needs. For more information, please visit https://www.oe-company.com/lasers/red-laser-diodes.html.

Ushio laser diodes

All Ushio high performance laser diodes are available from the Optoelectronics Company. Please contact the Optoelectronics Company to request samples for testing.


Ushio’s laser diode collection offers wavelengths across UV (375–405 nm), red (630–690 nm), and NIR (705–852 nm), with prospective optical output powers from 5 mW to 3,500 mW. Our LD collection has low and high power lasers, with low-operating currents, long lifespans, and efficiency, all while remaining 100% RoHS-compliant.

Ushio’s Epitex division has grown into the largest collection of light emitting diodes on the market. Covering all violet, visible, and infrared wavelengths, from 365 nanometres (nm) to 1,750 nm, this vast catalogue creates a one-stop-shop for single and multi-wavelength LEDs.

https://www.ushio.eu/ , https://swir-led.com/

About The Optoelectronics Company Ltd

The Optoelectronics Company is a manufacturer of custom-designed and standard laser diode modules and laser diode collimators. It is also an authorised distributor and supplier of Ushio Laser Diodes and LEDs, OSRAM laser diodes and Panasonic Aspherical Glass Lenses to customers worldwide.

contact details

For more information about the Optoelectronics Company please visit our website at www.oe-company.com or contact us at: Green End Farm, Wood End Green, Henham, Hertfordshire, CM22 6AY, UK, tel: +44 (0) 1279 851851, email: info@oe-company.com.


This news release is issued in accordance with clause 1.2j of the British codes of advertising and sales promotion and therefore cannot be subject to a transaction of any kind.