New silicate glasses for optoelectronics

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New silicate glasses for optoelectronics
Institute of chemical technology in Prague

• Faculty of chemical technology
• Department of glass and ceramics

Frantiek Lahodný, Martin Míka
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• Integrated optic devices
• - active or passive
• - splitters, couplers, waveguides amplifiers,
  gratings

- fabrication by ion exchange method - NaltgtAg
, or NaltgtK - direct laser beam writing method
on photosensitive glass
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Why silicate glass ?

• high mechanical durability
• chemical stability
• low cost
• better compatibility with today's used systems
  (refractive index, material dispersion, )

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Samples fabrication

• Weight out the raw materials with 0,0001g
  accuracy
• Homogenization for 20 minutes in mortar
• Melting in Pt-Rh crucibles with the lid at 1480C
• Casting of the melted glass into the iron form
• Controlled annealing
• Cutting and polishing for optical quality

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Samples homogeneity

• Small 15g samples have bad homogeneity
• Perspective compositions were melted in amount of
  100g with Pt stirring device

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I. research area

• - Laser active silicate glasses with different
  Er and Ybconcentrations
• - better gain without pumping laser power
  enhancement
• - improve excitation energy transfer on active
  element Er by co-doping partner Yb
• - photoluminescence intensity enhancement in
  1535nm region
• - find the optimal glass matrix chemical
  composition and Er/Yb ratio
• - chemical composition effect on glass
  properties, absorption
• and emission bands width, life time
• - undesirable phenomena concentration
  quenching,clusters formation

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Energy transfer on Er a Yb atoms
4I11/2
4I13/2
4I15/2
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Absorption spectrums for glasses with different
Yb content

• For result gain of the waveguide amplifier is
  important the value of the cross-sections (CS)
• - absorption CS express the pumping efficiency
• - emission CS express the probability measure
  of the stimulated emission
• Additional important properties is lifetime of
  the excited state
• We have studied the influence of the chemical
  composition on dynamic viscosity and thermal
  expansion

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Waveguide amplifier gain measurement
Experimental setup for waveguide amplifier gain
measurement
38 mm long planar waveguide amplifier fabricated
byion exchange method (Na?Ag) have6,7dB gain
at 1537nm
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II. Research area

• Development of the germanate-silicate glass with
  photosensitivity properties
• Photosensitivity discovered in 1978 by Dr.
  Kenneth Hill- local refractive index change
  after irradiation in order Dn 10-5-10-2 caused
  by structural fails and disorders Color centers
  model
• - EPR spectroscopy employed for estimation of
  the paramagnetic centers E(Ge) concentration,
  which cause the refractory index changes

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EPR measurement and results

• The sample is irradiate by middle-pressure Hg
  discharge lamp ( l 240 nm)and EPR spectrum is
  collected
• EPR signal of the E(Ge) has own characteristic
  spectroscopic constant, g- factor (for Ge g
  1,99049), it can be uniquely determined in the
  spectrum

Ge-paramagnetic center formation by photochemical
process
3,59
App
3,51
1800
3600
Time t s
Signal intensity changes during and after
irradiation
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UV lamp switch off
Increase and decrease of the E(Ge) signal
intensity during time
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Resume I. part

• We found perspective laser active silicate glass
  doped with Er and Yb
• We fabricated functional planar channel waveguide
  amplifier with high gain

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Resume - II. part

• We prepared silicate and borosilicate glasses
  with different content of Ge
• For best glass increase of the E(Ge) centers
  concentration is up to 530 and decrease only 9
  after irradiation, refractive index change
  Dn10-2 its very promising
• Further optimalization and measurements in plan

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Thank you for your attention