The Physics of Lasers

Fig. 4.1

Electromagnetic spectrum of radiations
In the visible and invisible infrared spectrum of light, we find the majority of the wavelengths used in dentistry (Fig. 4.2).

A335384_1_En_4_Fig2_HTML.gif
Fig. 4.2

Lasers in the electromagnetic spectrum of the light

4.3 Classification of Dental Lasers in the Electromagnetic Spectrum of Light [3]

A classification of lasers considers their position on the electromagnetic spectrum of light according to the wavelength :

  • Laser in the ultraviolet spectrum
  • Laser in the visible spectrum
  • Laser in the near-infrared spectrum
  • Laser in the mid-wavelength infrared spectrum
  • Laser in the far-infrared spectrum (Table 4.1)

    Table 4.1

    Classification of lasers according to their wavelength position on the electromagnetic spectrum of light
    Ultraviolet
    Visible
    Near infrared
    Medium infrared
    Far infrared
    Excimer 308 nm
    Blue diode 445 nm
    Diode 810 nm
    Er,Cr:YSGG 2780 nm
    CO2 9300 nm
     
    Argon
    Blu 470-488 nm
    Green 514 nm
    Diode 940 nm
    		  
    CO2 9600 nm
           
    CO2 10,600 nm
     
    Green KTP 532 nm
    Diode 970 nm
    		    
     
    Red diode 635–675 nm
    Diode 1064 nm
    Nd:YAG 1064 nm
    Er:YAG
    2940 nm
    		  
       
    Nd:YAP 1340 nm
    		    
Another classification identifies the main applications of specific lasers in:

  • Laser for soft tissue applications, laser for hard and soft tissue applications (also called all-tissue laser), laser for low-level therapy, and laser for diagnosis (Table 4.2).

    Table 4.2

    Classification of dental lasers according to clinical applications
    Soft tissue lasers
    Hard and soft tissue lasers
    LLLT
    Diagnosis
    Diodes 445 > 1064 nm
    Er,Cr:YSGG
    Er:YAG
    Diodes 445 > 1064 nm
    405 nm 655 nm
    Nd:YAG, Nd:YAP
    CO2 9300 nm
    		  
    CO2 10,600 nm
    		  
  • Another distinction considers the low-power lasers and the high-power lasers.

4.4 Properties of Laser Light [3]

Light is an electromagnetic radiation which, besides its wave characteristic, has a photonic corpuscular characteristic that transports a defined amount of energy (quantum). A laser device is able to deliver (aim) an elevated quantity of energy in a limited space in the form of light radiation, visible or invisible, generating the laser light.
Laser light is different from ordinary light due to a number of characteristics:

  • It is collimated, that is to say, it has a “one way” direction, thanks to the spatial coherence of emitted photons.
  • It is coherent, that is to say, every photon has the photon phase which determines the emission kept in time and space.
  • It is monochromatic, that is to say, there is just one visible color and just one wavelength.

4.5 Basic Components of Lasers [3]

A laser is composed of several basic elements for the generation and emission of the laser beam. The principal elements of a laser are:

  • Optical resonator (or optical cavity)
  • Active medium
  • Source of energy (or pumping source)
  • Controller (or microprocessor)
  • Cooling system
  • Delivery system
  • Handpiece and tips

4.5.1 Optical Cavity

It is a cavity which contains the active medium and two mirrors located at its extremities, one completely reflective and the other partially reflective and permeable. Photons, emitted by the excitement of the active medium (stimulation), are reflected inside the optical cavity and pass through the active medium many times, amplifying their energy via a waterfall phenomenon (amplification), before exiting (coming out from) the partially permeable mirror.

4.5.2 Active Medium

It is the heart of a laser. The active medium can be solid, liquid, gas, or a semiconductor (diode) and determines the specific wavelength of different lasers; its name identifies different lasers. The atomic population of the active medium, excited by an external source of energy, supplies the electrons for energetic transition from one orbit to another, which produces the emission of laser photons (Table 4.3).

Table 4.3

Reports the active medium of lasers most used in dentistry
Laser
Abbreviation
Active medium
Hosting medium
Doping atom
Wavelength (nm)
Argon
Ar
Gas
–
–
488 and 514
Carbon dioxide
CO2
Gas
–
–
9300; 9600 and 10,600
Diode
–
Semiconductor
–
–
445, 635–810 940–980–1064
Potassium titanyl phosphate
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Sep 10, 2016 | Posted by in Endodontics | Comments Off on The Physics of Lasers

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