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 3a
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

1. Adatto MA, Amir R, Bhawalkar J, et al. New and Advanced Picosecond Lasers for Tattoo Removal. Curr Probl Dermatol. 2017;52:113–123. 
2. Wang CC, Sue YM, Yang CH, Chen CK. A comparison of Q-switched alexandrite laser and intense pulsed light for the treatment of freckles and lentigines in Asian persons: a randomized, physician-blinded, split-face comparative trial. J Am Acad Dermatol. 2006;54(5):804-810.
3. Bernstein EF, Schomacker K, Paranjape A, Jones CJ. Pulsed dye laser treatment of rosacea using a novel 15 mm diameter treatment beam. Lasers Surg Med. 2018;50(8):808–812. 
4. Artzi O, Mehrabi JN, Koren A, Niv R, Lapidoth M, Levi A. Picosecond 532-nm neodymium-doped yttrium aluminium garnet laser-a novel and promising modality for the treatment of café-au-lait macules. Lasers Med Sci. 2018;33(4):693–697. 
5. Koren A, Niv R, Cohen S, Artzi O. A 1064-nm Neodymium-doped Yttrium Aluminum Garnet Picosecond Laser for the Treatment of Hyperpigmented Scars. Dermatol Surg. 2019;45(5):725–729. 
6. Levin MK, Ng E, Bae YS, Brauer JA, Geronemus RG. Treatment of pigmentary disorders in patients with skin of color with a novel 755 nm picosecond, Q-switched ruby, and Q-switched Nd:YAG nanosecond lasers: A retrospective photographic review. Lasers Surg Med. 2016;48(2):181–187. 
7. Torbeck RL, Schilling L, Khorasani H, Dover JS, Arndt KA, Saedi N. Evolution of the Picosecond Laser: A Review of Literature. Dermatol Surg. 2019;45(2):183–194. 
8. Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation. Science. 1983;220(4596):524–527. 
9. Data on file, Candela, 2018.
10. PicoWay 510(k) clearance (K191685), September, 2019.