Ultra-long pulse technology utilizes a principle of thermodynamic differentiation to separate the target from the surrounding tissue. By extending the laser energy delivery over hundreds of milliseconds, the device operates well beyond the thermal relaxation time (TRT) of the epidermis, which is typically only 3 to 10 milliseconds. This timing mismatch allows the skin to dissipate absorbed heat into the surrounding tissue and cooling window before thermal damage can occur, while the hair follicle—due to its larger volume—continues to accumulate the heat required for destruction.
Core Takeaway Ultra-long pulse technology creates a safety gap by delivering energy slower than the skin’s cooling rate but faster than the hair follicle’s heat loss rate. This ensures the epidermis stays cool while the follicle retains enough energy to be effectively destroyed.
The Physics of Thermal Relaxation
To understand how this technology protects the skin, one must look at the specific thermal properties of the biological targets involved.
The Epidermal Baseline
The "thermal relaxation time" (TRT) is the time required for a target tissue to dissipate 50% of the heat it has absorbed.
For the epidermis (the outer layer of skin), this time is extremely short. According to primary technical data, the epidermal TRT ranges from roughly 3 to 10 milliseconds.
The Cooling Window
Ultra-long pulse technology stretches the pulse duration to hundreds of milliseconds.
Because this duration is significantly longer than the epidermal TRT, the skin does not hold onto the heat. As the laser energy is delivered, the epidermis is simultaneously shedding that thermal energy into surrounding tissues or surface cooling agents.
Mechanisms of Follicular Destruction
While the skin is successfully cooling itself during the long pulse, the hair follicle reacts differently due to its physical structure.
Volumetric Heat Accumulation
Hair follicles are significantly larger and deeper structures than the melanin-rich layers of the epidermis. Consequently, they possess a much longer thermal relaxation time.
While the epidermis sheds heat rapidly, the hair follicle retains it. Even over the extended duration of an ultra-long pulse, the follicle cannot dissipate the energy as fast as it receives it.
Thermodynamic Differentiation
This creates a divergence in temperature between the two tissues.
The epidermis remains below the threshold of thermal damage because its "input" (laser energy) is balanced by its "output" (cooling/dissipation).
Simultaneously, the hair follicle experiences a net gain in thermal energy. It continues to accumulate heat until it reaches the critical temperature required for coagulation or vaporization of the hair structure.
Understanding the Trade-offs
While ultra-long pulse technology offers superior safety profiles, it is vital to understand the thermodynamic balance to ensure efficacy.
The limit of "Ultra-Long"
The pulse must be long enough to protect the skin, but not so long that the hair follicle also has time to cool down.
If the pulse width becomes excessive relative to the hair's thickness, the follicle might dissipate heat too efficiently, failing to reach the destruction threshold.
Targeting Fine Hair
Finer hair has a shorter TRT than thick hair.
Therefore, when using ultra-long pulses (hundreds of milliseconds), there is a theoretical risk that very fine hair may cool down too quickly to be destroyed effectively compared to coarse, terminal hair.
Making the Right Choice for Your Goal
Understanding the interplay between pulse duration and tissue relaxation times allows for safer, more customized treatments.
- If your primary focus is Epidermal Safety: Prioritize ultra-long pulse durations, as they allow the skin maximum time to dissipate heat and prevent surface burns.
- If your primary focus is Thick/Deep Hair: The ultra-long pulse is highly effective, as the large volume of the follicle will continue to accumulate heat long after the skin has cooled.
Ultimately, the efficacy of ultra-long pulse technology lies in its ability to exploit the time-lag between how quickly skin cools versus how long hair holds heat.
Summary Table:
| Feature | Epidermis (Skin) | Hair Follicle |
|---|---|---|
| Thermal Relaxation Time (TRT) | Short (3–10 ms) | Long (due to larger volume) |
| Reaction to Ultra-Long Pulse | Dissipates heat rapidly | Accumulates heat continuously |
| Thermal Outcome | Remains below damage threshold | Reaches coagulation temperature |
| Primary Benefit | Maximum surface safety | Targeted follicular destruction |
Elevate Your Clinic’s Safety and Results with BELIS
At BELIS, we specialize in professional-grade medical aesthetic equipment designed exclusively for clinics and premium salons. Our advanced laser systems, including Diode Hair Removal, CO2 Fractional, Nd:YAG, and Pico lasers, leverage cutting-edge technology like ultra-long pulses to ensure superior epidermal protection and clinical efficacy.
Whether you are looking for body sculpting solutions like EMSlim and Cryolipolysis or specialized care devices such as HIFU, Microneedle RF, and Hydrafacial systems, BELIS provides the precision your business demands.
Ready to upgrade your practice with industry-leading technology?
Contact Us Today to Consult with an Expert
References
- Eric P. Smith, E. Victor Ross. Modified Superlong Pulse 810 nm Diode Laser in the Treatment of Pseudofolliculitis Barbae in Skin Types V and VI. DOI: 10.1097/00042728-200503000-00008
This article is also based on technical information from Belislaser Knowledge Base .
Related Products
- EMSlim Body Sculpting Machine EMS Body Slimming Machine
- IPL SHR+Radio frecuency machine
- 12D HIFU Machine Device for Facial HIFU Treatment
- Clinic Use IPL and SHR Hair Removal Machine with Nd Yag Laser Tattoo Removal
- 7D 12D 4D HIFU Machine Device
People Also Ask
- Does Emslim really work? Yes, for Sculpting Muscle, Not Just Burning Fat
- How many sessions of ultrasonic liposuction are needed? Achieve Optimal Body Contouring
- What are the steps for using an EMS slimming machine? Professional Guide for Optimal Body Contouring Results
- How do HIFEM devices achieve muscle building and fat reduction? Master the Science of Supramaximal Contractions
- Is EMSlim safe? Ensuring Your Safety in Non-Invasive Body Contouring
