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www-g.eng.cam.ac.uk/cosmos COSMOS is a Basic Technology Research Grant funded by the EPSRC, EP/D04894X Tuning the wavelength of emission in organic semiconducting lasers by the orientation of a liquid crystalline conjugated polymer M.H. Song, B. Wenger, R.H. Friend Optoelectronics group, Cavendish Laboratory , University of Cambridge. 1. We can get the difference between aligned and unaligned F8 film due to different n eff . (different wavelength) 2. We can get lower threshold value by aligning F8 molecules. - Maximizing absorption (effective number of excitons) - Maximizing the amount of the emitted radiation waveguided (transition dipole moment) 3. We can tune the wavelength of lasing by changing the angle between the grating line and the orientation of the polymer molecules in the aligned F8 film. (different refractive index(n eff )). Conclusions Comparison between isotropic and anisotropic F8 layers in DFB structures ragg wavelength, Λ: Grating period m: The Bragg order n eff : The effective refractive index of waveguide structure • First order grating (m=1) : band edge emission • Second order grating (m=2) : Surface emission Substrate Polyimide F8 =2n eff •Λ/m Tunable lasers 440 450 460 470 480 490 500 0 20000 40000 60000 454.5 471.4 466.5 460.2 0 o In ten sity (a.u .) W avelen g th (n m ) 15 o 30 o 40 o 0 10 20 30 40 1.63 1.64 1.65 1.66 1.67 1.68 1.69 1.70 456 460 464 468 472 n eff A n g le b etw e e n g ra tin g lin e a n d o rie n ta tio n o f F 8 ( o ) W avelen g th (n m ) 0 20 40 60 80 100 445 450 455 460 465 470 475 480 0 10000 20000 30000 40000 50000 60000 In ten sity (a.u .) T h resh o ld ( J/cm 2 ) W a v e le n th (n m ) Grating line n (Above) (a) Schematic of tunable DFB F8 laser sample cell. (b) Lasing spectra measured for the anisotropic F8 laser sample cell with different angles between grating line and the orientation of F8. (c) Lasing wavelengths and effective refractive index of the anisotropic F8 laser sample cell as a function of angles between grating line and the orientation of F8. (d) Threshold energy as a function of laser wavelength for the anisotropic F8 laser sample cell with different angles between grating line and the orientation of F8. (a) (c) (b) (d) TE 0 TE 1 50 100 150 200 250 440 450 460 470 480 490 500 50 100 150 200 250 1.5 9 1.6 2 1.6 5 1.6 8 1.7 1 1.7 4 1.7 7 1.8 0 an iso tro p ic F 8 iso tro p ic F 8 W avelen g th (nm ) T h ic kn e s s (n m) n e ff 430 440 450 460 470 480 0 10000 20000 30000 40000 50000 60000 70000 461 458 82nm 78nm 448.80 445.53 In te n s ity (a .u .) W a v e le n g th (n m ) 147nm 173nm 430 440 450 460 470 480 490 0 20000 40000 60000 85nm 78nm 62nm 57nm 46nm 449.23 454.23 458 461 4 68 .7 2 In te n s ity (a .u .) W avelen g th (n m ) 400 450 500 550 0 2000 4000 6000 8000 10000 0 o 4 o 8 o 13 o 495.3 446 In te n s ity (a .u .) W a v e le n g th (n m ) (Above) Lasing spectra measured (a) for the anisotropic F8 laser sample cell and (b) for the isotropic F8 laser sample cell with various film thickness of F8 layer. (c) A few photoluminescence spectra of -polarized waveguide, and insect show the effective index vs wavelength for, waveguide modes in a 193nm-thick aligned F8 film. (d) Lasing wavelengths and effective refractive index of the anisotropic F8 laser sample cell (black-filled triangles) and the isotropic F8 laser sample cell (red-open circles) as a function of F8 film thickness. (a) (c) (b) (d) Cavendish Laboratory (Above) (a) Schematic of the four different excitation configurations. (b) TE-polarized emission spectra from the anisotropic F8 laser cell (the polarization beam is parallel to the F8 chain alignment) with 62nm thickness for pump energies above and below threshold. (c) Threshold behavior in the anisotropic F8 laser cell. The polarization beam parallel (perpendicular) to the F8 chain alignment corresponds to case 1 (case 2). (d) Threshold behavior in an isotropic F8 laser cell. The polarization beam parallel (perpendicular) to the F8 chain alignment corresponds to case 3 (case 4). How do DFB lasers work?
description
Grating line. q. F8. Polyimide. Substrate. TE 0. TE 1. n. ( b). ( a). ( d). ( c). Tunable lasers. - PowerPoint PPT Presentation
Transcript of Document
www-g.eng.cam.ac.uk/cosmos
COSMOS is a Basic Technology Research Grant funded by the EPSRC, EP/D04894X
Tuning the wavelength of emission in organic semiconducting lasers by the orientation of a liquid crystalline conjugated polymer
M.H. Song, B. Wenger, R.H. Friend
Optoelectronics group, Cavendish Laboratory , University of Cambridge.
1. We can get the difference between aligned and unaligned F8 film due to different neff. (different wavelength)
2. We can get lower threshold value by aligning F8 molecules.
- Maximizing absorption (effective number of excitons)
- Maximizing the amount of the emitted radiation waveguided
(transition dipole moment)
3. We can tune the wavelength of lasing by changing the angle between
the grating line and the orientation of the polymer molecules in the
aligned F8 film. (different refractive index(neff)).
Conclusions
Comparison between isotropic and anisotropic F8 layers in DFB structures
ragg wavelength, Λ: Grating periodm: The Bragg orderneff : The effective refractive index of waveguide structure• First order grating (m=1) : band edge emission• Second order grating (m=2) : Surface emission
Substrate
Polyimide
F8
=2neff•Λ/m
Tunable lasers
440 450 460 470 480 490 5000
20000
40000
60000 454.5 471.4466.5460.2 0o
Inte
nsi
ty (
a.u
.)
Wavelength (nm)
15o
30o
40o
0 10 20 30 401.63
1.64
1.65
1.66
1.67
1.68
1.69
1.70
456
460
464
468
472
nef
f
Angle between grating line and orientation of F8 (o)
Wav
elen
gth
(n
m)
0
20
40
60
80
100
445 450 455 460 465 470 475 4800
10000
20000
30000
40000
50000
60000
Inte
nsi
ty (
a.u
.)
Th
resh
old
(J
/cm
2 )
Wavelenth (nm)
Grating line
n
(Above) (a) Schematic of tunable DFB F8 laser sample cell. (b) Lasing spectra measured for the anisotropic F8 laser sample cell with different angles between grating line and the orientation of F8. (c) Lasing wavelengths and effective refractive index of the anisotropic F8 laser sample cell as a function of angles between grating line and the orientation of F8. (d) Threshold energy as a function of laser wavelength for the anisotropic F8 laser sample cell with different angles between grating line and the orientation of F8.
(a)
(c)
(b)
(d)
TE0
TE1
50 100 150 200 250
440
450
460
470
480
490
500
50 100 150 200 250
1.59
1.62
1.65
1.68
1.71
1.74
1.77
1.80 anisotropic F8 isotropic F8
W
ave
len
gth
(n
m)
Thickness (nm)
ne
ff
430 440 450 460 470 4800
10000
20000
30000
40000
50000
60000
70000461458
82nm 78nm
448.80
445.53
Inte
nsi
ty (
a.u
.)
Wavelength (nm)
147nm
173nm
430 440 450 460 470 480 4900
20000
40000
60000 85nm 78nm 62nm 57nm 46nm
449.23
454.23 458461 468.72
Inte
ns
ity
(a
.u.)
Wavelength (nm)
400 450 500 5500
2000
4000
6000
8000
10000 0o
4o
8o
13o495.3
446
Inte
nsi
ty (
a.u
.)
Wavelength (nm)
(Above) Lasing spectra measured (a) for the anisotropic F8 laser sample cell and (b) for the isotropic F8 laser sample cell with various film thickness of F8 layer. (c) A few photoluminescence spectra of -polarized waveguide, and insect show the effective index vs wavelength for, waveguide modes in a 193nm-thick aligned F8 film. (d) Lasing wavelengths and effective refractive index of the anisotropic F8 laser sample cell (black-filled triangles) and the isotropic F8 laser sample cell (red-open circles) as a function of F8 film thickness.
(a)
(c)
(b)
(d)
CavendishLaboratory
(Above) (a) Schematic of the four different excitation configurations. (b) TE-polarized emission spectra from the anisotropic F8 laser cell (the polarization beam is parallel to the F8 chain alignment) with 62nm thickness for pump energies above and below threshold. (c) Threshold behavior in the anisotropic F8 laser cell. The polarization beam parallel (perpendicular) to the F8 chain alignment corresponds to case 1 (case 2). (d) Threshold behavior in an isotropic F8 laser cell. The polarization beam parallel (perpendicular) to the F8 chain alignment corresponds to case 3 (case 4).
How do DFB lasers work?
