The truth about available wavelengths for picosecond systems: Are pulses really picoseconds?

Picosecond technology has revolutionized laser treatment by minimizing thermal impact to surrounding tissues. Short picosecond pulse durations result in a primarily photoacoustic, rather than thermal effect, reducing the risk of hypo-hyper pigmentation and scarring.^1-3 The efficacy and safety of picosecond systems in tattoo removal, in particular for patients with skin of color, has led to wider use in other skin conditions involving dyspigmentation, as well as other aesthetic uses such as acne scarring and wrinkles.^4-7

This increased interest in picosecond technology raises the question of how to differentiate between available systems. The ideal system has a range of useful picosecond wavelengths and the ability to consistently generate an ultra-short, high-energy pulse for each of these wavelengths.

Systems designed to generate true picosecond pulses are better able to provide consistent, high energy, single-peak, picosecond pulses. Because the efficacy and safety of picosecond treatment is tied to both selective thermolysis and a pulse duration shorter than or comparable to the stress confinement time leading to a predominately photo-acoustic effect, the delivery of consistent, high-energy, ultra-short pulses across all device wavelengths is integral to treatment outcome. 

For the PicoWay system¹⁰, pulse energy at each wavelength is consistently high with a variability ranging from 0.5 to 4.0% (Figure 1). In contrast, as demonstrated by system evaluations, the difference between expected and delivered energy in competing systems may vary by up to 40%.⁹ In addition to consistently delivering high-energy pulses, the PicoWay system also consistently delivers an ultra-short pulse width across all wavelengths (250 to 450ps; Figure 2), with a pulse width variance of between 9 and 24%.⁹ In contrast, competing systems have pulse width variance of up to 194%, at times with multiple peaks within a delivered pulse.⁹

Figure 1

Figure 2

Additional oscilloscope data support the above findings and confirm that the PicoWay system consistently delivers high-power, single-peak pulses at both 1064 and 532 nm (Figure 3).⁹

Figure 3.A. The PicoWay system consistently delivers high-power, single-peak pulses at 1064nm.

Figure 3.B. The PicoWay system consistently delivers high-power, single-peak pulses at 532nm.

In contrast, pulses generated by other systems have low peak power, multi-peak pulses, and/or wide, nanosecond pulse widths.  The range of pulse configurations at 1064nm is shown in (Figure 4). These same patterns, including low energy and multiple peaks were also observed at 532nm.⁹

Figure 4: Systems adapted to provide picosecond pulses may provide weak pulses (A), multiple peaks (B-D) and overall inconsistent performance (Measures at 1064nm).⁹

Figure 4.A. 960ps

Figure 4.B. Subpulse: 634ps, Effective: 1.06ns

Figure 4.C. Subpulse: 421ps, Effective: 965ps

Figure 4.D. Subpulse: 1.761ns, Effective: 4.091ns

The wide variation observed for many of the tested devices is cause for concern, as pulse width, peak power, and delivery of the specified wavelength are drivers of treatment outcome.⁸ Overall, these findings indicate that systems designed as picosecond systems have more reliable output across wavelengths and are more likely to deliver the peak energy and pulse width claimed by the manufacturer.⁹

When researching picosecond systems, it is important to evaluate system features beyond the level of “available” wavelengths and price. The value afforded by true picosecond pulses at all wavelengths is clear when one considers the importance of offering consistent and low downtime treatments with minimal risk of hyper/hypopigmentation across multiple aesthetic indications.

Learn more about the PicoWay system