Time of flight for photon in human skin

Antra Dzerve,Inesa Ferulova,Alexey Lihachev,Janis Spigulis

doi:10.18287/jbpe16.02.030301

Antra Dzerve, Inesa Ferulova + Show 2 more

Open Access

https://doi.org/10.18287/jbpe16.02.030301

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Abstract

The time of flight for photons in human skin was measured using picosecond diode laser. Two different wavelength lasers were used - 405 nm and 510 nm. A difference for time of flight in normal skin and in nevus was observed as well as a difference for different wavelength laser irradiation was observed. For 405 nm laser irradiation the difference was 41 ps while comparison of time of flights skin and nevi using 510 nm irradiation showed a result of 32 ps. Results allow to conclude that the time photon travels in skin might depend on the characteristics of the medium and wavelength of the irradiation. This can be related to known data for light penetration depth in human skin for different wavelengths.

Highlights

Skin is by far the largest organ for humans and it is the one that comes in contact with many threats from outside world all the time – air pollution can clog pores and create rash or zits, too much time spent in the sun can result in sunburns, UV irradiation can be a cause of diseases
For 405 nm laser irradiation the difference was 41 ps while comparison of time of flights skin and nevi using 510 nm irradiation showed a result of 32 ps
Results allow to conclude that the time photon travels in skin might depend on the characteristics of the medium and wavelength of the irradiation

Summary

Introduction

Skin is by far the largest organ for humans and it is the one that comes in contact with many threats from outside world all the time – air pollution can clog pores and create rash or zits, too much time spent in the sun can result in sunburns, UV irradiation can be a cause of diseases. Optical diagnostics as a fast and relatively easy way for diagnosing skin diseases is getting more popular. By time of flight one understands the time photon spends in skin before it is reflected back and exits the skin. When light enters the skin, part of it is reflected back from the surface, but part of it continues to penetrate deeper layers of skin. This light can be scattered, absorbed or reflected in many different directions.

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