Within the Q-switched laser family, the 694nm and 755nm wavelengths each possess distinct physical characteristics and clinical indications. Compared with 1064nm, these two wavelengths exhibit notable differences in pigment absorption, penetration depth, and clinical application—making a clear understanding of their properties essential for precise treatment.

1. 694nm Wavelength: Strong Pigment Absorption for Superficial to Mid‑Dermal Lesions

The 694nm wavelength falls within the deep red spectrum, offering higher melanin absorption than 755nm with relatively lower blood absorption, and penetrating to the superficial to mid-dermal layers.

Indications:

• Café-au-lait spots and epidermal pigmentation: Delivers superior results compared to 532nm, making it a preferred option for epidermal pigmentary lesions.

• Light-colored dermal pigmentation: Suitable for superficial dermal pigment issues in lighter-skinned patients.

Operational Notes:

Fluence and endpoint responses at 694nm are relatively more challenging to gauge. Treatment readily produces mild frosting—a faint grayish-white appearance. While this serves as a marker of efficacy, it also signals the need for careful dose control to avoid overtreatment.

2. 755nm Wavelength: Predominantly Picosecond, Nanosecond Q-Switched Less Common

The 755nm wavelength falls within the near-infrared spectrum. In current clinical practice, it is most commonly delivered via picosecond lasers; nanosecond Q-switched 755nm systems are relatively uncommon in the market.

Indications:

• Light-skinned patients with light-colored inherited dermal pigmentation: For genetically determined dermal pigmentary lesions that are lighter in color (such as certain Ota nevus subtypes), 755nm or 694nm may be prioritized.

• Green-blue tattoo pigments: Both 694nm and 755nm—deep red and near-infrared lasers—are well suited for treating tattoos dominated by green and blue ink.

3. Comparison with 1064nm: Penetration Depth Defines Indication Boundaries

Both 694nm and 755nm have shallower skin penetration than 1064nm, resulting in relatively limited efficacy in the following scenarios:

• Inherited dermal pigmentation (Ota nevus in Asian skin): 1064nm offers a distinct advantage due to deeper penetration.

• Dark dermal pigmentation and blue‑black tattoos: 1064nm is similarly more effective.

Endpoint Reference:

When treating dark dermal lesions and blue‑black tattoos, immediate grayish‑white discoloration and mild frosting serve as indicators of adequate response; subsequent erythema, purpura, or even mild pinpoint bleeding and crusting are considered normal therapeutic responses.

4. Matching Wavelength to Skin Type

For patients with darker skin types (Fitzpatrick III‑V) , the 1064nm wavelength offers superior safety and efficacy due to its relatively lower epidermal melanin absorption and deeper penetration—making it the more appropriate choice. In contrast, 694nm and 755nm are better suited for lighter‑skinned patients.