Various Laser Applications with especial emphasis on material processing (laser cutting, laser welding,laser drilling) anf Laser Eye surgery.....

1. APPLICATION OF LASERS IN
CUTTING,WELDING,DRILLING AND EYE SURGRIES
Presented by:
Ajay Singh
Physics Department
Indian Institute of Technology Delhi

2. Heating
Cooling
Imaging
Communicati
on

3. Laser processing of materials (Sadhana Vol. 28, Parts 3 & 4, June/August 2003, pp. 495–562)

5. Laser–matter interaction in material processing
 laser–matter interaction within the near-surface region achieves extreme heating
and cooling rates (103–1010 K/s), while the total deposited energy (typically, 0·1–
10 J/cm2) is insufficient to affect, in a significant way, the temperature of the bulk
material. This allows the near-surface region to be processed under extreme
conditions with little effect on the bulk properties.
 Laser Heating:Coupling of laser radiation to electrons within the metal. Energy high
but per photon energy < work function of the material.

6.  Energy absorption
 Spatial distribution of
deposited energy
 Heating due to laser
irradiation

7. LASER Cutting
 Either using a transmissive (glass) or reflecting (metal mirror) optics.
 The transmissive optics is made of ZnSe, GaAs or CdTe lenses for CO2
lasers or quartz lenses for YAG or excimer lasers. (LASER damage threshold
)….
 The reflective optics consists of parabolic off-axis mirrors. The main
constituents for control and monitoring are the lasers with shutter control,
beam guidance train, focusing optics and a computer controlled translation
stage to move the work-piece.
 Wavelengths 1.064µm (Nd-YAG), 10.6µm or 9.4µm(CO2 )

9.  High power CO2 lasers or Nd:YAG lasers
 Both pulse and continuous wave modes
 Mechanical punching is fast but is limited to holes further than 3 mm diameter.
 Electro chemical machining is too slow at 180 s/hole but does give a neat
hole.
 Electro discharge machining is expensive and slow at 58 s/hole. Electron
beam
drilling is fast at 0·125 s/hole but needs a vacuum chamber and is more
expen
sive than aYAG laser processing. In comparison, aYAG laser takes 4 s/hole
to
outsmart all other methods [1].
LASER Drilling

11.  Laser joining is applicable to inorganic/organic and similar/dissimilar materials
with an extremely high precision, versatility and productivity that can only be
matched by electron beam welding. Moreover, laser welding can be done in air,
unlike the vacuum processing needed in electron beam welding. In comparison
to conventional or arc welding, laser welding scores several advantages like
narrow welds with controlled bead size, faster welding with a higher productivity,
less distortion, narrow heat affected zone, amenability to welding Al/Mg alloys
and dissimilar materials, and minimum contamination.
 pulsed or continuous wave Nd:YAG or CO2 laser (very seldom ruby laser, too)
are the commonly used lasers for joining. The main process variables in laser
welding are laser power, beam diameter, beam configuration, travel speed of the
work-piece, substrate condition (roughness, temperature), filler type/feed rate,
alloy composition and thermophysical properties of the work piece.
LASER Welding
Figure : Schematic of laser welding without a filler rod (front
view) . The argon shroud removes heat and prevents
undue oxidation. The relative position of the laser focus
determines the quality and configuration of the weld.[2]

12. Source: http://www.uslasercorp.com/envoy/welding.html

13. Refractive Eye Surgery
Refractive eye surgery is eye surgery used to improve the refractive
state of the eye and decrease or eliminate dependency on glasses or
contact lenses. This can include various methods of surgical remodelling
of the cornea or cataract surgery. The most common methods today use
excimer lasers to reshape the curvature of the cornea. Successful
refractive eye surgery can reduce or cure common vision disorders such
as myopia, hyperopia and astigmatism, as well as degenerative
disorders like keratoconus.
In Laser surgery surgery, the curvature of the cornea is altered by
removing a specific amount of corneal tissue with ultraviolet photo-
ablation from the excimer laser.
http://ildenaro.it/blog/2014/02/27/riparazione-della-cornea-al-monaldi-il-laser-supervoloce/

14.  1950’s – Columbian Jose Barraquer developed Microkeratome
& keratomileusis techniques and discovered root causes for eye
trauma
 1970’s – Russian Svyatoslav Fyodorov developed Radial
Keratotomy (and posterior chamber implantable contact lenses
in 1980)
 1970’s – Development of Excimer Laser (origin of LASEK laser)
 1982 – 3 Members of the IBM research team discovered the
laser could be used to remove biological tissue without heat
damage to surrounding tissue
 1987 – Dr. Steven Trokel performed the 1st laser surgery on a
patients eye
 1996 – Lasik Eye Surgery became officially approved by the
U.S. government
BRIEF HISTORY

15. CLASSIFICATION
REFRACTIVE SURGERIES
CORNEA BASED LENTICULAR BASED COMBINED(BIOPTICS)
-R.K.
-PRK
-LASIK/Intra
LASIK
-EPILASIK
-LASEK
-Conductive
Keratoplasty
-Corneal Inlays
and rings
-Clear Lens
extraction for
myopia
-Phakic IOL
- Prelex Clear
Lens Extraction
with use of
Multifocal IOL’s
Combination
of the two

16.  A) Radial keratotomy (RK)
 B) Excimer laser photorefractive keratectomy ( PRK )
 C) Laser assisted in situ keratomiliuses (LASIK)
 D) Laser assisted subepithelial keratomiliuses ( LASEK )
 E) Laser thermokeratoplasty (LTK )
 D) Intracorneal ring segments (ICRS)
 G) Phakic intraocular lenses (IOLs )

17. Various types of laser surgery are used to treat refractive error:
 LASIK : knife is used to cut a flap in the cornea, and a laser is used
to reshape the layers underneath, to treat refractive error.
 IntraLASIK: a variant in which the flap is also cut with a laser
Photorefractive keratectomy (PRK, LASEK), in which the cornea is
reshaped without first cutting a flap
 Laser thermal keratoplasty: in which a ring of concentric burns is
made in the cornea, which cause its surface to steepen, allowing
better near vision

18. Various types of laser surgery are used to treat refractive error:
 LASIK : knife is used to cut a flap in the cornea, and a laser is used
to reshape the layers underneath, to treat refractive error.
 IntraLASIK: a variant in which the flap is also cut with a laser
Photorefractive keratectomy (PRK, LASEK), in which the cornea is
reshaped without first cutting a flap
 Laser thermal keratoplasty: in which a ring of concentric burns is
made in the cornea, which cause its surface to steepen, allowing
better near vision
Lasers are also used to treat non-refractive conditions, such as:
 Phototherapeutic keratectomy (PTK), in which opacities and surface
irregularities are removed from the cornea
 Laser coagulation, in which a laser is used to cauterize blood
vessels in the eye, to treat various conditions
 Lasers can be used to repair tears in the retina.

19.  Types of lasers used-
 Excimer-Excited dimer of two atoms
-An inert gas(Argon)
-Halide(Fluoride)
which releases ultraviolet energy at193nm for corneal ablation
 Non-Excimer solid state lasers-
 210nm Q switched diode pumped laser
 213 nm Q switched diode pumped laser(Pulsar)

20.  Types of lasers used-
 Excimer-Excited dimer of two atoms
-An inert gas(Argon)
-Halide(Fluoride)
which releases ultraviolet energy at193nm for corneal ablation
 Non-Excimer solid state lasers-
 210nm Q switched diode pumped laser
 213 nm Q switched diode pumped laser(Pulsar)
 Advantage of Non-Excimer solid state lasers-
 No toxic excimer gases
 Wavelength closer to absorption peak of corneal collagen—less
thermal and collateral damage
 Better pulse to pulse stability
 Not absorbed by air, water, tear fluid-so less sensitive to humidity or
room temperature
 No purging with inert gases required.

23. PROCEDURE
Step 1 : Creating corneal flap
Step 2 : Folds the flap back and perform
laser procedure which corrects
vision .

25. EXAMPLES OF CORRECTION

26.  The surgery is typically done within 30 minutes or less
-quick & painless
 Most people achieve 20/20 vision (or even better) afterwards (90% reach
desired vision after LASIK)
 May still need glasses/contact lenses, but prescription is much lower
than before
 A small percentage of people have an enhancement (minor touch up)
surgery later for further improved vision
 Requires no bandages or stitches
 Research conducted by the Magill Research Center for Vision
Correction, Medical University of South Carolina, showed that the overall
patient satisfaction rate after primary LASIK surgery was 95.4%. They
further differentiated between myopic LASIK (95.3%) and hyperopic
LASIK (96.3%). They concluded that the vast majority (95.4%) of patients
were satisfied with their outcome after LASIK surgery.
ADVANTAGES OVER NON-LASER SURGERIES

27.  Some patients lose vision.
 Some patients develop debilitating visual symptoms.
 You may still need eyeglasses after surgery.
 Some patients may develop severe dry eye syndrome.
 For some farsighted patients, results may diminish with age.
 Long-term data is not available.
Potentials Risks
Also The LASER eye surgery is not for you if you are
 You required a change in your contact lens or glasses prescription in the
past year. This is called refractive instability.
 You have a disease or are on medications that may affect wound healing.
 You actively participate in contact sports. You participate in boxing,
wrestling, martial arts or other activities in which blows to the face and
eyes are a normal occurrence.
But Still the success rate > 95%, further
improvements going on

28. Works Cited
http://en.wikipedia.org/wiki/Refractive_surgery
http://www.worldoflasers.com/laserapplindustrial.htm
http://en.wikipedia.org/wiki/LASIK
http://www.firstlight-laser.com/about.html
http://en.wikipedia.org/wiki/Laser_surgery#Eye_surgery
http://ildenaro.it/blog/2014/02/27/riparazione-della-cornea-al-monaldi-il-laser-supervoloce/
http://www.powershow.com/view/14b8bb-ZjY4N/Lasers_in Manufacturing_
http://www.uslasercorp.com/envoy/welding.html
http://laneconference.org/downloads/IndustrialContributions/LANE2014_Naeem_Flexible
_laser_system.pdf
Other references:
[1]. SteenW M (ed.) 1991 Laser material processing (NewYork: Springer Verlag)
[2]. Laser processing of Materials “J DUTTA MAJUMDAR and I MANNA ”(S¯adhan¯a
Vol. 28, Parts 3 & 4, June/August 2003, pp. 495–562)
[3]. T. Juhasz, G. Djotyan,F. H. Loesel*R. M. Kurtz*C. Horvath* J. F. Bille***, and G.
Mourou* “Applications of Femtosecond Lasers in Corneal Surgery” (Laser Physics, Vol.
10, No. 2, 2000, pp. 495–500.)
[4] Boulnois, J.-L., 1986, Lasers in Medical Science, 1, 47.
[5] Niemz, M.H., 1996, Laser Tissue Interactions: Fundamentals and Applications
(Heidelberg: Springer).
[6] Rykalin N N, Uglov A, Kokora A 1978 Laser machining and welding (Moscow: Mir)

29. Thanks
For
Your Kind Attention