Online proceedings - EDA Publishing Association

increased.
11-13
May 2011, Aix-en-Provence, France
Power meter
LD@1553nm
collimator
3.6μm
2.5μm
MMF-fiber
(a)
1mm/s
(b)
2mm/s
(c)
3mm/s
Fig. 4 Fabrication with various scanning speeds at E = 170 mW and
d = 10 μm
3.6μm
(a)
5mm/s
3.7μm
(d)
8mm/s
3.3μm
(b)
6mm/s
3.3μm
(e)
9mm/s
2.3μm
(c)
7mm/s
2.5μm
(f)
10mm/s
Fig. 5 Fabrication with various scanning speeds at E = 170
mW and d = 0 μm
The laser power was increased to 230 mW to modify fused
silica 10 μm in depth. Scanning speed should be increased to
avoid surface ablation. The results in Fig. 5 show that the
fused silica is ablated given scanning speeds between 5 mm/s
and 7 mm/s; and modified widths of3.7μm, 3.3μm and 2.5μm
correspond to scanning speeds of 8 mm/s, 9 mm/s and 10
mm/s, proving that the fused silica can be modified at different
depths through focusing and tuning the laser power and
scanning speed.
2. Waveguide propagating loss measurement
Fig. 6 shows the system for measuring waveguide
propagating loss. The system conducts the laser diode (LD,
center wavelength = 1553 nm) to the waveguide layer on the
XYZ-rotation stage. In the end of waveguide layer, the
collimator couples the multi-mode optic fiber to the power
meter for acquiring and analyzing signal. The results show
that the propagating loss are 4.6 dB/cm、4.8 dB/cm、6.2
dB/cm as the scanning velocities are 8 mm/s, 9 mm/s and 10
mm/s, respectively, with 230 mW and 10 μm of depth. It
indicates that the increased scanning velocity causes the
larger energy loss due to the low absorbing energy of fused
silica.
XYZ-rotation
stage
Transmission (dBm)
0
-5
-10
-15
-20
-25
-30
-35
-40
LD
-45
1553.2 1553.4 1553.6 1553.8 1554.0 1554.2
Wavelength (nm)
Fig. 6 The system for measuring waveguide propagating loss
Table 2 Fabrication parameters of waveguide using
femtosecond laser
Laser
power
E
(mW)
170
230
Scanning focusing
velocity depth
NF
results
v
s d
(KJ/cm 2 )
(mm/s) (μm)
1
ablation 7.191
2 ablation 3.596
3 ablation 2.397
4 0 ablation 1.798
5 waveguide 1.438
6 waveguide 1.198
7 waveguide 1.027
5
ablation 1.946
6 ablation 1.621
7 ablation 1.390
10
8 waveguide 1.216
9 waveguide 1.081
10 waveguide 0.973
3. Waveguide discussion
The laser power, the diameter of the laser beam, the
scanning speed and the rate of repetition are all very
influential factors in laser machining. This study analyzes the
machining performance with NF factor [10], as shown below.
2ω0
PRF
NF =
(5)
vs
where ω is the minimal radius of the laser beam, R = 1
0
MHz is the repetition rate, and E
F p
= is the average
2
Rπω 0
fluence per lasing. In this study, the laser wavelength, λ , is
532 nm. The focus distance of the lens, f , is 20 mm. The
diameter of the incident laser, D, is 5 mm. The ω is 1.5 μm,
0
estimated by the 1.05 of the measured laser beam quality
factor ( D
M
2 πω0
= ). E is the laser power. Substituting these
2λf
parameters into Eq.(5), the range of the NF value is 1.438 –
0.973 KJ/cm 2 , indicating the range of fabrication energy of
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