Table 1.

Main benefits and limitations of coherent (laser) and non-coherent (LED, lamp) light sources in superficial PDT. The table is adapted from [8].

Light Source	Main Benefits	Limitations
Laser (coherent)	<0.1 nm spectral bandwidth High power Efficient coupling to optical fibres Uniform irradiance can be easily achieved Adaptive emission (VCSEL, Edge-emitting laser) Faster modulation than LEDs Possibility for ultra-short pulses (fs-regime)	Expensive High maintenance Bulkier than an LED Less choice of wavelengths
LED (non-coherent)	Low cost Small Adaptive emission (SLED, ELED) Used for whole-body or point treatment LEDs can fit down biopsy channels permitting deep-seated PDT	5–10 nm spectral bandwidth (FWHM) Large beam divergence Thermal effects for I-PDT (low electro-optical conversion efficiency)
Lamp (non-coherent)	Low cost Simple design Wide illumination field Multi-wavelength irradiance	UV and NIR radiation (optical filtering is needed) Large beam divergence High coupling losses with light guides