DIODE LASER MECHANISM OF ACTION

SCIENCE OF LASER DELIVERY IN DIODE LASER IN LASER DENTISTRY

1. DEFINING DIODE LASERS, THEIR MECHANISM OF LASING, ADVANTAGES AND DISADVANTAGES AND PERSPECTIVES FOR THE FUTURE? DR. FEBEL HUDA , M.D.S,DICOI,FICOI,FAD,DLD,FOI . ORAL MAXILLOFACIAL PROSTHODONTIST AND IMPLANTOLOGIST DIPLOMATE FROM THE INTERNATIONAL CONGRESS OF ORAL IMPLANTOLOGY FELLOW FROM THE INTERNATIONAL CONGRESS OF ORAL IMPLANTOLOGY DIPLOMATE IN LASER DENTISTRY (UNIVERSITY OF GENOVA - ITALY) FELLOW IN AESTHETIC DENTISTRY (UNIVERSITY OF GREIFSWALD - GERMANY) FUNDAMENTALS IN ORAL IMPLANTOLOGY (UNIVERSITY OF BUFFALO –USA)

2. DEFINITION A semiconductor laser diode is a device capable of producing a lasing action by applying a potential difference across a modified p-n junction . This modified p –n junction is heavily doped and contained within a cavity, thus providing the gain medium for the laser . A feedback circuit is also implemented in order to control the amount of current sent to the laser diode.

3. MECHANISM OF LASING

4. MECHANISM OF LASING There are basically three processes for interaction between a photon and an electron Optical Absorption Spontaneous Emission Stimulated Emission

5. MECHANISM OF LASING (band-gap diagram- optical absorption) Eg = band gap energy

6. MECHANISM OF LASING (band-gap diagram- optical absorption)

7. MECHANISM OF LASING (band-gap diagram- spontaneous Emission) The spontaneous emission occurs in a random direction and yields a spectral output with a fairly wide bandwidth

8. MECHANISM OF LASING (band-gap diagram- Stimulated Emission)

9. MECHANISM OF LASING (band-gap diagram- population inversion) Since Ec lesser than Ev

10. MECHANISM OF LASING (band-gap diagram)

11. MECHANISM OF LASING (Optical Resonant Cavity)

12. MECHANISM OF LASING (Requirements O f L aser) Direct band-gap P opulation inversion Optical resonant cavity

13. MECHANISM OF LASING (Basic-Requirements Of Laser)

14. MECHANISM OF DIODE LASING (P-N Junction)

15. MECHANISM OF DIODE LASING (Forward Bias)

16. MECHANISM OF DIODE LASING (Doping)

17. MECHANISM OF DIODE LASING (Semiconductors Used)

18. TYPES OF DIODE LASER Homojunction laser Hetrojunction laser Double Hetrojunction Quantum well laser Quantum cascade laser Distributed feedback lasers VCSELs (vertical cavity surface emitting laser VECSELs ( vertical external cavity surface emitting laser)

19. MECHANISM OF DIODE LASING (Homo-junction, Energy B and D iagram) " Fermi level " is the term used to describe the top of the collection of electron   energy levels  at absolute zero temperature.

20. MECHANISM OF DIODE LASING (Homo-junction, Energy Band Diagram)

21. MECHANISM OF DIODE LASING (Homo-junction, Energy Band Diagram) If forward bias increased into sufficient large voltage

22. MECHANISM OF DIODE LASING (Homo-junction, disadvantage) High threshold current required for lasing High temperature is produced Can not operate in continuous mode Low efficiency

23. MECHANISM OF DIODE LASING (Hetrojunction)

24. MECHANISM OF DIODE LASING (Hetrojunction) Hetrojunction are of three types of band-gap design, TYPE 1 : STRADDLING GAP TYPE 2 : STAGGERED GAP TYPE 3 : BROKEN GAP

25. MECHANISM OF DIODE LASING (Double - Hetrojunction)

26. MECHANISM OF DIODE LASING (Double – Hetrojunction, Band-gap D iagram)

27. MECHANISM OF DIODE LASING (Double – Hetrojunction, Quantum W ell, Band-gap Diagram)

28. MECHANISM OF DIODE LASING (Double – Hetrojunction, Quantum cascade, Band-gap Diagram) Electrization of electrons between layers of the semiconductor

29. MECHANISM OF DIODE LASING (Double – Hetrojunction, DFB – Distributed feedback laser) Diffraction grating Quantum wells Selectively reflecting only one wave length

30. MECHANISM OF DIODE LASING (Double – Hetrojunction, VCSELs – Vertical – cavity surface-emitting laser)

31. MECHANISM OF DIODE LASING (Double – Hetrojunction, VCSELs – Vertical – cavity surface-emitting laser)

32. MECHANISM OF DIODE LASING (Double – Hetrojunction, VCSELs – Vertical – cavity surface-emitting laser) Distributed brad reflector Quantum confinement effect

33. MECHANISM OF DIODE LASING (Double – Hetrojunction, VCSELs)

34. MECHANISM OF DIODE LASING (QUANTUM DOT AND WIRE)

35. MECHANISM OF DIODE LASING (QUANTUM DOT AND WIRE)

36. Advantage of VCSEL The structure can be integrated into two-dimensional array configuration Low threshold currents enable high-density arrays Surface- normal emission and nearly identical to the photo detector geometry give easy alignment of the packaging Circular and low divergent output beams eliminate the need for corrective efficiency Low-cost potential because the devices are completed and tested at the wafer level Lower temperature- sensitivity compare to edge-emitting laser diodes High transmission speed with low power consumption.

37. ADVANTAGE AND DISADVANTAGE OF DIODE LASER A wavelength with wide spectrum of usage Excellent hemostasis (blood less field) Bactericidal Swelling and edema is comparatively very minimal Painless or minimal discofort recorded Detoxification Removal of smear layer Can be delivered in pulses Compact Delivery system not as expensive as hard tissue lasers Helps better CAD/CAM scan by providing a bloodless field in regions close to the gingiva Expensive Poorly absorbed in hard tissue and hydroxyapatite

38. PERSPECTIVES FOR THE FUTURE Peri implantitis – LLLT Prostrate cancer – BPH ( short healing and hospitalization) Ossiointergration – LLLT TMJ pain therapy – LLLT chronic traumatic brain injury (TBI) were treated with transcranial LEDs. Laser diodes emitting in the 800-980nm range have been used for kidney and brain tumors ablation Laser implant osteotomy Sleep apnea / anti snoring therapy- Nightlase ® ( fotona ) Anesthesia – frequency of laser in same frequency of nerve – depolarization of nerve in SSP mode Activate medication similar to PDT Selective ablation of periodontal bacteria Depth perception

39. Reference History and development of semiconductor lasers by Valleri.k.kononenko , DOI:10.13140/RG.2.1.2729.9288 IEEE Journal of quantum electrics vol.QE-22,No.9,September.1986 Distribution feedback laser diodes and optical tunable filters by H. Ghafouri Shiraz Education in laser dentistry: a necessity, an optional extra, or an irrelevence ?, steven parker , J Laser Dent 2009;17(2): 104-105. The practical use of laser in general practice, Roshkind DM, Alpha Omegan 2008;101(3):152 -161. Diode laser and CAD/CAM dentistry : perfect marriage of two advanced technology, Eugene L Antenucci , J Laser dent 2009;17(2):100-103. Versatility of an 810 nm Diode Laser in Dentistry: An Overview, Samo Pirnat , Journal of Laser and Health Academy;Vol . 2007; No. 4;1-9. Effects on oral soft tissue produced by a diode laser in vitro. Goharkhay K, Lasers Surg Med. 1999; 25(5 ): 401-406.