Page 278 - Optofluidics Fundamentals, Devices, and Applications

252 Cha pte r T e n

refractive index of the mixture is determined by the experimentally
verified linear extrapolation between the two pure solvents [12].
In these experiments, the emission wavelength of a third-order DFB
laser (with estimated FSR of 291 nm at the third-order Bragg
reflectance) is tuned between 580.60 nm and 587.35 nm by changing
the refractive index of the dye solution from 1.43 to 1.485.
The efficiency of microfluidic or refractive index tuning is
limited by the spatial overlap between the optical mode and

Intensity (counts)
16000
12
Threshold energy: 159 nJ
14000 Threshold fluence: 0.80 mJ/cm 2
10
12000 8
Output energy (a.u.) 6 FWHM < 0.1 nm
10000
8000
6000 4
2
4000
0
2000 0 200 400 600 800 1000
Absorbed pump energy (nJ) x100
0
450 460 470 480 490 500 510 520 530 540 550 560 570 580 590 600 610 620 630 640 650
(a)
Rh6G Rh101
1
0.9
0.8
Normalized laser power 0.6
0.7

0.5
0.4
0.3
0.2
0.1
0
550 560 570 580 590 600 610 620 630 640 650
Wavelength (nm)
(b)

FIGURE 10-6 Panel (a) shows a lasing spectrum and input-output characteristic
(inset) from the liquid-core waveguide DFB laser illustrated in Fig. 10-1c. Panel (b)
shows tuning curves for the laser obtained with two different laser dyes, rhodamine
6G and rhodamine 101 [Z. Li and D. Psaltis, “Optofluidic Distributed Feedback Dye
Lasers,” IEEE J. Top. Quant. Electron. 13(2), 185–193 (2007)].