In recent years, the application of optical technology in the field of medical cosmetology has been expanding, and it has been widely used as a new safety method in acne treatment, which can effectively treat acne in multiple wavelengths, but it also has its limitations:

1) Blue-green light – the effect varies from person to person

In the visible wavelength band, blue and green light can oxidize the photosensitive porphyrin produced by Epidermobacterium acnes, killing bacteria and reducing inflammation, but the effect varies from person to person, and bacterial resistance in some patients can lead to a decrease in efficacy. Blue light does not penetrate enough depth and is only effective for mild to moderate inflammatory acne. During the green light test, there is a phenomenon of acne rebound.

2) Red light – cannot be completely eradicated

The penetration effect of red light is relatively good, but it still cannot completely inhibit deep inflammation.

3) Short-wave infrared - need to cooperate with local anesthesia or cooling system

Short-wave infrared (SWIR) lasers are more penetrating and can penetrate deep into the sebaceous glands and hair follicles, using the photothermal effect of the laser to directly destroy the sebaceous glands and acne bacilli in the cells, and its long-term effect is better. At present, the clinical trials of 1064nm laser and 1540nm laser have shown certain effects, but in the trial, it was found that it is necessary to use a local anesthetic or cooling system, otherwise the patient needs to suffer severe pain, permanent erythema on the face, and even direct epidermal damage.

4) Photodynamic Therapy (PDT) – burning, stinging, and need to avoid light

PDT requires the application of photosensitizing drugs (ALA, etc.) to the lesion site, and by irradiating the site with a specific wavelength, the photosensitizer can be activated to produce reactive oxygen species, causing damage and even death of the diseased cells. For stubborn acne, PDT is more effective, but the activation of the photosensitizer may cause burning and stinging, and the residue of the photosensitizer requires the patient to avoid light for a period of time.

Effective, safe, long-lasting, painless treatment options:

1726nm laser treatment

In order to further simplify the treatment plan, avoid the risk of pain, and reduce the treatment burden of patients, the industry hopes to find a treatment option that does not require photosensitizing drugs and acts directly on the sebaceous glands instead of other cell tissues. At present, the 1726nm wavelength laser has been shown to be able to selectively transfer light energy to specific target chromophores in the sebaceous glands, where the absorption coefficient of the sebaceous glands is much higher than that of water, and the short and high-power pulse energy can precisely destroy the sebaceous gland structure while reducing thermal damage to the surrounding tissues. The wavelength of 1726nm can penetrate to 1.5mm under the skin and directly act on the deep sebaceous glands to reduce the occurrence of acne from the root.

Fig.1 Absorption coefficients of water and sebum in the mid-infrared band^【1】

Numerical simulation and in vivo experiments have confirmed that under the condition of controlling pulse energy and pulse time, this band laser can locally increase the temperature of the sebaceous gland to more than 60 °C, so that the gland can be irreversibly damaged, and directly inhibit the excessive secretion of sebum, while the epidermal temperature only rises below 42 °C, which further protects the epidermis, reduces the discomfort of treatment and side effects such as postoperative erythema and edema, and ensures safety.

Fig.2 Histological skin image: no obvious damage to the epidermis (A), complete (B) and partial (C) thermal damage to the sebaceous gland, and (D) undamaged sebaceous gland^【2】

A number of clinical studies have shown that the 1726nm laser is effective for mild, moderate and severe acne, and the number of inflammatory lesions can be reduced by 50% after 3 treatments, and the efficacy can still be maintained in the long-term follow-up after 24 months, as shown in Figure 3. At the same time, the efficacy and safety of the 1726nm laser for different skin types (including dark skin tones) were consistent, with only transient erythema or edema after surgery, no serious adverse reactions, and patients tolerated the treatment well. The 1726 nm laser selectively targets the sebaceous glands through its unique photothermal mechanism of action, providing an efficient, safe, and long-lasting solution for acne treatment. With its significant targeted action, wide skin adaptability, extremely low side effects and high patient satisfaction, it has become a pioneer in acne treatment and has shown significant competitiveness in the field of medical aesthetics.

Fig.3 Clinical photos of a 24-year-old female subject at baseline pretreatment (A) and 6 (B), 21 (C) and 35 (D) months after the fourth treatment^【2】

Everbrihght uses self-developed high-power indium phosphide chips, combined with self-developed module automatic assembly equipment based on active alignment (AA) technology, and launches a 365μm fiber core diameter 1726nm wavelength locking fiber-coupled laser for the medical beauty industry, with a continuous output power of more than 100W, Figure 4 shows the power curve at the cooling temperature of 25°C, and the laser electro-optical conversion efficiency exceeds 20%.

Fig.4 Continuous output power curve of 1726 nm wavelength-locked fiber-coupled laser

The product is locked at 1726±1.5nm and the spectral width (FWHM) is <1.5nm, which can achieve wavelength locking at start-up and wavelength locking from the threshold current to the operating current range, Figure 5(A) shows the locking effect of different currents during continuous operation, and the cooling temperature is 25°C. The product achieves wavelength locking from 10 to 40°C, and Figure 5(B) shows the locking effect of changing the refrigeration temperature when the power supply is 16 A continuous. The wavelength drift coefficient of this product is 0.012nm/°C, which is significantly better than similar products.

Fig.5 The wavelength locking effect of the 1726 nm laser continuously outputting time-varying current (A) and variable temperature (B).

The product also achieves wavelength locking in pulsed operating mode. Figure 6 shows the wavelength locking effect of 70% duty cycle (pulse width 35 ms), duty cycle 50% (pulse width 25 ms), duty cycle 30% (pulse width 15 ms), and duty cycle 10% (pulse width 10 ms) at 25°C cooling.

Fig.6 Wavelength locking effect of 1726nm laser under different duty cycle conditions

Everbright

Changguang Huaxin is committed to the research and development and production of semiconductor laser chips, the core technology covers the core field of the semiconductor laser industry, overcomes the technical problems such as epitaxial growth, cavity surface treatment, packaging and fiber coupling that have been shackled, and has built a complete process platform and mass production line from chip design, MOCVD (epitaxy), FAB wafer tape-out, cleavage/coating, packaging, testing, optical coupling, direct semiconductor laser, etc., with 2-inch, 3-inch, and 6-inch mass production lines. With two major product structures, GaAs gallium arsenide, InP indium phosphide and GaN gallium nitride, it is one of the few IDM semiconductor laser companies in the world with 6-inch wire epitaxy, wafer manufacturing and other key process production capabilities.

References:

【1】     Matteo G.S., Amogh K., Michael K., A novel 1726‑nm laser system for safe and efective treatment of acne vulgaris. Lasers in Medical Science (2022) 37:3639–3647.

【2】     Emil A.T, Rafael S, Michael E et al, Treatment of Acne With a 1726 nm Laser, Air Cooling,and Real‐Time Temperature Monitoring, Software‐Assisted Power Adjustment to Achieve a Temperature Endpoint With Selective Sebaceous Gland Photothermolysis. Lasers in Surgery and Medicine(2025):1-16.