1. Laser Spectroscopy and its applications Changwon National University
Department of Physics
Changwon National University
Jang Kiwan

2. Light and Atoms/Ions ☞ Color of Light ⇔ Frequency of Light.
☞ Atoms / molecules interacts with light of certain frequencies.
 It is called the atom’s resonant frequencies.
☞ Absorption Bandwidth of an atom.
 Homegeneous Linewidth (same for all “like” atoms.)
☞ Local effects can shift the resonant frequencies
 Even for otherwise identical atoms.
☞ Absorption profile of a collection of atoms
 Inhomgeneous linewidth (due to shifts of “like” atoms)

3. Optical Transition Frequency [R.E. in Host] 1. Homogeneous linewidth
Dynamical perturbations on the optical transition frequency.
: lattice phonons, fluctuating nuclear or electrons spins.
 Information on dynamical processes interacting with the optically active ions.
Frequency
absorption
Time domain- Photon echo, OFID, etc.
(B) Frequency domain- Hole burning, FLN, etc.

4. Optical Transition Frequency
2. Inhomogeneous linewidth.
 Probability distribution of homogeneous single ion packets.
 Static lattice strains inherent in all samples.
 Small fraction of a wave number to many hundreds of wave number.
Frequency
absorption
Absorption spectrum, Emission spectrum etc.

5. Experimental Techniques in Spectroscope
Photon Echo : Two Pulses Photon Echo
B. Spectral Hole Burning
1. Hole lifetime :
☞ Temporary spectral hole burning.
☞ Persistent spectral hole burning(PSHB).
2. Hole burning method :
☞ One color hole burning or self gated hole burning.
☞ Two color hole burning or photon gated hole burning.
C. Decay time, Rise time measurement
D. PL (CL, EL) Intensity, Excitation and Emission spectrum, Quantum
Efficiency, Color Coordinate etc.,

6. What is a spectral holeburning?
Interference filter: nm
Optical Memory, Very narrow optical filter etc.,

7. Application of Persistent Spectral Hole Burning
A. Optical Memory
Frequency domain storage  Nf
Spatial storage  Nx • Ny• Nz
Total storage density  Nx • Ny • Nz•Nf
B. Very Narrow Band Pass Optical Filter
Interference filter: nm

8. Application of Permament Spectral holeburning
1. Binary Information Recording
☞ Paten ted By Szabo (transient holes ) and Castro et al.,
(persistent holes)
☞ Presence(absence) of a hole ⇒Encode a digital “1” (or “0”).
☞ Surface density ⇒Limited by the diffraction of the light.
☞ Most optimistic estimation ⇒ 1014 bit/cm2.
CD: ~107 bit/cm2.
2. Analog Information Recording
☞ Four-dimensional (spatial-temperal) holograph on the basis
of spectral holeburning.
3. Narrow-band transmission filter:
☞ ~order of 10-3 cm-1.
☞ Insenstive to the incident angle.
☞ Simply tuning of the transmission wavelength.
☞ Easily manufactured for complex transmission profiles.
※ Best interference filter: ~300 cm-1.

9. Phenomena probed by Persistent Holeburning Spectral hole property
Temperature dependence of Hole width
Dephasing mechanism-phonon, TLS
Time dependence of Hole Width
Spectral diffusion
Laser induced hole filling, erasing effects
Amorphous host dynamics, Photochemical mechanism
Shifts and splittings in external fields
E-field: Stark effect
H-field:Zeeman effect
Degeneracy of transition
Strain filed: stress
Coupling coeff.,: symmetry
Side hole positions
Vibronic and other excited state splitting
Anti hole positions
Ground state splitting

10. Two wavelength holeburning
1. Photon gated Transition
Gated Trap State
Primary Excited State
2. Spontaneous
Decay
Read/Write/Data
Lasers
Decay
Trap State
Ground State
※ Without Trap states, Data Lifetime is an excited state Lifetime.

11. Periodic Table Ln3+ electronic configuration = [Xe]4fN
Lanthanides N=
Ln3+ electronic configuration = [Xe]4fN
Lanthanide chemistry nearly identical for all members of series
since they have the same [Xe] outer (bonding) electrons

12. Energy level of Activator (Rare Earth Ions)
Manganese, Z=25
☞ Ground state electron configuration: [Ar]3d54s2
☞ Shell Structure: 2,8,13,2
☞ Term Symbol: 6S5/2
▣ Mn2+- 3d5 Transition
▣ Broad Spectrum
1S2
2S2 2P6
3S2 3P63d54S2

13. Energy level of Activator (Rare Earth Ions)
Europium, Z=63
Ln3+ [Kr]4d105s25p64fN
☞ Ground state electron configuration: [Xe]4F76s2
☞ Shell Structure: 2,8,18,25.8.2
☞ Term Symbol: 8S7/2
SrAl2O4:Eu2+
4f-4f
Eu3+ [Kr]4d105s25p64f6
▣ 4f-4f level Transition
▣ Narrow Spectrum: Shielded by 5s/5p
5D0 → 7F2
Gd2O3: Eu3+
1S2
2S2 2P6
3S2 3P64S23d10
4P6 5S2 4d105P6
6S24f7

14. Shielding of the 4f electrons by the outer 5s and 5p electrons
Ln3+ [Xe]4d105s25p64fN 5s 5p

15. Effects of Confinement
A. Semiconductors
☞ Confinement of the delocalized electronic wavefunction.
☞ Leads to increase in the bandgap and changes in the exciton spectrum.
☞ Dependence of emission color on size of CdSe nanoparticles.
Emitted photon
shifts to the blue
Decrease in size
Han et al. Nature, Biotechnol. 19, 631 (2001)

16. Dynamical Processes
Relaxation
1. Population relaxation time = T1
(time for excited population to decay)
This has two components: the rates are additive
(1) Radiative transitions to all lower levels ☜ relax. time = τrad
(2) Non-radiative processes (phonons,
energy transfer, etc.)
☜ relax. time = τnr
Population decay rate = T1-1 = τrad-1 + Tnr-1
2. Dephasing = T2
processes that interrupt the phase of the excited state
Γhom = (1/2π) T (1/π) T2-1
Excited
state
Ground
State
τrad-1
τnr-1

17. Energy Level Diagram for Eu3+ in a crystal field
~100 cm-1
~1000 cm-1
δ1g
δ2g
0.001 cm-1
δ1e
δ2e
Free ion
Crystal Field
Quadrupole+pseudoquadrupole
~2000 cm-1

18. Two Y3+ symmetry sited in Y2O3C2
C3i
C2: C3i=3:1
: Yttrium
: Oxygen
: Vacancy Diagonal

19. Hole Spectra for the samples prepared with different method
anti holes
Side hole
5D0-7F0 transition

20. White LED - Phosphors Applications for white phosphor coated LEDs
RGB LEDs
Potentially highest efficiency.
Tunable white point.
High cost.
Blue LED + Yellow phosphors
Simple
Decent color rendering (Ra ~ 75)
UV-LED + RGB phosphors
White point determined by phosphors only.
Excellent color rendering.

21. Studied samples and Experimental Tools
A. Studied samples
① Y2O3:Eu3+ Bulk, micron and submicron powder, nano powder.
② SrB4O7:Sm2+ and SrB6O10:Sm(2+,3+) powder crystal.
③ Mg0.5 Sr0.5FCl0.5 Br0.5:Sm2+ powder crystal.
④ KSrPO4:Eu2+ codoped with Mn2+ powder crystal.
⑤ SrZn2(PO4)2 : Eu2+, Mn2+ powder crystal.
⑥ NaCaPO4: Eu(3+,2+) and NaCaPO4: Tb3+ powder crystals.
⑦ Gd2O3:Eu3+ Nano tube and nano wire powder crystals.
B. Experimental Tools ☞ Spectral holeburning, Photon echo, Absorption and Emission
spectroscopy, Thermal Luminscence, XRD etc.,
☞ Time resolved Spectroscopy.

22. Sample Preparation by Solid State Reaction Technique
옥사발에서 1시간 동안
혼합 및 분쇄
곱게 갈린 시료를 알루미늄
도가니에 넣어 공기 중 900℃
1시간 동안 1차 열처리
254nm 파장의 자외선을
비추어, SrAl2O4:Eu3+에
의한 발광을 확인
시료준비
1차 열처리가 끝난 시료를
다시 알루미늄 도가니에 넣어
2차 열처리 준비
수소-질소 분위기 중
1100℃ 4시간 동안
2차 열처리
365nm 파장의 자외선을
비추어, SrAl2O4:Eu2+에
의한 발광을 확인

23. Spectrum of Eu2O3 Nanoparticles
The spectrum is that of the monoclinic phase of Eu2O3 which can be made in bulk form at high pressure
There are three sites (A,B, and C) for the Eu3+ ion in this phase
The inhomogeneous linewidths broaden as the nanoparticle size decreases
The broadening indicates the environment of the Eu3+ ions varies from site to site due to:
(1) disorder in the nanoparticle
(2) location near the surface which may have more strains or defects
Excitation spectrum A B C
5D0
7F0

24. Two Examples of Optical Uses of Nanoparticles
1. Förster Resonant Energy Transfer (FRET)
antibody
antigen
Wang et al Nano Lett. 2, 817 (2002)

25. Two Examples of Optical Uses of Nanoparticles
2. Imaging of human cells using rare earth-doped tri-calcium phosphate (apatite) nanoparticles with a confocal laser scanning microscope
Eu3+
5D1
5D0
laser
luminescence
7F2
7F0

26. Mg0.5Sr0.5FCl0.5Br0.5 : Sm2+ mixed Crystals
MgF2 + SrCl2 * 6H2O + SrBr2 * 6H2O +Sm2O3
Sample No.
First heat treatment
Second heat treatment
Remark
M-air
1100 ℃ in air,1 hr No
Sm3+
M-H2
1100 ℃ in H2 ,1 hr NO
Sm2+
MH2-X10
X-ray irradiation , 10 hrs
MO-X10
1100 ℃ in air, 1 hr

27. PL Spectra of Mg0.5Sr0.5FCl0.5Br0.5 : Sm2+ mixed Crystals
Physical Reduction
Chemical Reduction

28. Absorption spectrum of M-H2 and MO-X10 Samples

29. Photo-bleaching effect of M-H2 and MO-X10 Samples

30. PL Spectra of SrB4O7:Sm2+ and SrB6O10:Sm(2+,3+)
Before X-ray Irradiation
After X-ray Irradiation
Sm3+ ions doped in SrB6O10 crystal were reduced into Sm2+ by x-ray irradiation.

31. Phtobleaching of Sm2+ doped in SrB4O7 and SrB6O10
SrB4O7 : Sm2+
SrB6O10 : Sm2+
Photo-bleaching effect of Sm2+ ions highly depended on the crystal structure after x-ray irradiation.

32. 3rd Heat-treatment Effect on PL of Sm2+ doped in SrB6O10

33. Optical Properties of Eu3+ doped in Gd2O3 nanotube and nanowire
1. XRD pattern of Gd(OH)3 보강 소멸
(100)
(210)
(110)

34. FE-SEM image of Gd(OH)3 nanotube powder
Optical Properties of Eu3+ doped in Gd2O3 nanotube and nanowire
FE-SEM image of Gd(OH)3 nanotube powder

35. Optical Properties of Eu3+ doped in Gd2O3 nanotube and nanowire
TGA & DTA Gd(OH)3

36. Optical Properties of Eu3+ doped in Gd2O3 nanotube and nanowire
XRD pattern
Heat treatment based on TGA & DTA Gd(OH)3
Gd(OH)3
Gd2O3

37. Optical Properties of Eu3+ doped in Gd2O3 nanotube and nanowire
FE-SEM of Gd2O3
X 100,000 확대
X 200,000 확대

38. Excitation and Emission spectra of Gd2O3:Eu3+ nanotube
Optical Properties of Eu3+ doped in Gd2O3 nanotube and nanowire
Excitation and Emission spectra of Gd2O3:Eu3+ nanotube

39. Optical Properties of Eu3+ doped in Gd2O3 submicronsphere
FE-SEM & EDS
직경: ~650 nm
Element
Wt%
At% OK
39.06
86.27
EuL
04.67
01.09
GdL
56.26
12.64
Matrix
Correction
ZAF

40. Ex & PL Spectrum- Gd2O3:Eu3+ submicronsphere
Optical Properties of Eu3+ doped in Gd2O3 submicronsphere
Ex & PL Spectrum- Gd2O3:Eu3+ submicronsphere

41. FE-SEM Gd(OH)3 :Eu3+nanowire
Optical Properties of Eu3+ doped in Gd2O3 nanowire
FE-SEM Gd(OH)3 :Eu3+nanowire
Optical Properties of Eu3+ doped in Gd2O3
1. Nanotube
2. Submicron sphere
3. Nanowire
4. Nanosphere

42. White Phosphor for UV-LEDs Technology of White Light based on LED

43. White Phosphor for UV-LEDs
White UV-LED phosphors
☞ High quantum efficiency
☞ High temperature stability.
☞ Single-phased white emitting phosphor : Research goal.
Compounds of ABPO4 (A = Li+, Na+, K+, Rb+, Cs+; B = Sr2+, Ba2+) :
☞ Excellent thermal and hydrolytic stability
☞ Tetrahedral rigid three dimensional matrix.
Prepared and studied samples:
☞ KSrPO4: Eu2+, Mn2+
① Eu2+, an efficient sensitizer transferring energy to Mn2+
② The ionic radii of Eu Å ~ Sr Å
Mn Å ~ Zn Å
☞ SrZn2(PO4)2 : Eu2+, Mn2+ (SZP: Eu2+, Mn2+)
☞ NaCaPO4: Eu2+
☞ NaCaPO4: Tb3+ : New green phosphor

44. White Phosphor for UV-LEDs
Technology Issue For white light LED
DOE SSL R&D Workshop 2011 San Diego, CA
☞ Lack of phosphors that meet the need of high efficiency at high power.
☞ Lack of phosphors that offer appropriate luminescence performance.

45. White Phosphor for UV-LEDs
Comparison of Current Phosphors for SSL
Phosphors
Quantum Yield
Thermal Stability (150 ℃)
Chemical Stability
Remark
YAG:Ce3+
~90%
~90 %
Stable
Yellow
(CaBaSr)2SiO4:Eu2+
~55 %
Unstable
Green
(CaSrBa)Si2N2O2:Eu2+
~70%
~80 %
Β-Sialon: Eu2+
~95 %
(SrBa)2Si5N8:Eu2+
~80%
~85 %
Red
(SrCa)AlSiN3:Eu2+
80~90%
85~93 %
(SrCa)S:Eu2+
~86 %
Reported by Lightscape Materials Inc.,
Color
Composition
Emission Peak
FWHM
Quantum
Yield
Thermal
Stability(150 ℃)
Red
Nitride nm
~94 nm
>85 %
~93 %
Green
Oxynitride nm
75~95 nm

46. White Phosphor for UV-LEDs Objectives for solid state light(SSL)
1. Quantumn Yield=90 %.
2. Thermal Quenching Loss<10%.
3. Luminescence Maintenance>90 % after 5,000 hours.
4. Scattering Loss<10%.
5. Cost-effective preparation processes.

47. White Phosphor for UV-LEDs
Thermal Stability of commercial phosphors
Reported by Lightscape Materials Inc.,
Nitride (Red) and
oxynitride(Green)
Commercial phosphor

48. White Phosphor for UV-LEDs
Warm white light for LED
1. SrCaSiO4:EU2+ prepared with flux
Sumitomo Metal Mining Co., Ltd (May 17, 2012)

49. Thank You !