1. Slow light in Photonic Crystals
Jana Jagerska, IPEQ-LOEQ

2. Jana Jagerska, IPEQ-LOEQ
Overview
Slow light in PhCs - the physics behind
Why is slow light interesting?
Challenges: bandwidth, losses, dispersion, coupling to the slow light modes
Devices for slow light operation
Characterization and measurement techniques
1/2/2019
Jana Jagerska, IPEQ-LOEQ

3. Jana Jagerska, IPEQ-LOEQ
The physics behind
Slow light effect - based on coupled resonances
PhC: slow Bloch modes , waveguides at cut-off (W1), mini-stopbands (W3)…
Spectral regions of “flat” dispersion
0.289
0.376
Coupled resonances between electron and photon in atomic gasses - electromagnetically induced transparency
Or resonance of optical modes in
1/2/2019
Jana Jagerska, IPEQ-LOEQ

4. Jana Jagerska, IPEQ-LOEQ
The physics behind
W1 waveguide:
Omnidirectional
reflection
Backscattering
1/2/2019
Jana Jagerska, IPEQ-LOEQ

5. Jana Jagerska, IPEQ-LOEQ
Why slow light?
Improved light-matter interaction
Intensity… scales with the slow- down factor
Nonlinear interactions, reduced control power in tunable devices…
Effective phase change enhancement (switches modulators)
Towards compact devices
Light delay
Towards optical buffers
1/2/2019
Jana Jagerska, IPEQ-LOEQ

6. Light-matter interaction
Spatial compression of light pulses upon entering the slow-light regime
Intensity enhancement
IDEAL CASE !
Phase-change enhancement
Small change of material index - abrupt change in phase
Compact & faster devices, low switching powers
1/2/2019
Jana Jagerska, IPEQ-LOEQ

7. Jana Jagerska, IPEQ-LOEQ
Challenges
Operation bandwidth
Dispersion
High propagation loss, effect of disorder
Coupling issues
Tunability …
1/2/2019
Jana Jagerska, IPEQ-LOEQ

8. Challenges: Bandwidth
Standard W1
‘Slow’ W1
Structures with moderate slowdown factor (vg = ) have several nm bandwidth around 1550 nm, corresponding to 1 THz or more
1/2/2019
Jana Jagerska, IPEQ-LOEQ

9. Challenges: Dispersion
Parabolic flat bands: large group velocity dispersion:
Distortion of pulse envelope
Nonzero vg, constant slope
Fast light
Slow light
1/2/2019
Jana Jagerska, IPEQ-LOEQ

10. Losses & coupling issues
Propagation loss scales with 1/ng2 for parabolic bands:
Increased light-matter interaction higher sensitivity to disorder
+ backscattering higher propagation loss
Fast mode
Slow mode
Coupling efficiency: mode transformers (tapers), crystal termination or both
1/2/2019
Jana Jagerska, IPEQ-LOEQ

11. Jana Jagerska, IPEQ-LOEQ
Device Concepts
Y.A. Vlasov et al., “Active control of slow light on a chip with photonic crystal waveguides”, Nature 438, pp.65-68, 2005.
M. Notomi et al., Extremely large group velocity dispersion of line-defect waveguides in photonic crystal slabs”, PRL 87, (2001)
Slow-light modulator
1/2/2019
Jana Jagerska, IPEQ-LOEQ

12. Jana Jagerska, IPEQ-LOEQ
Device Concepts
T. Baba, D. Mori, J. Phys. D 40, 2659, (2005)
Shifting of an ideal band using a chirped structure
GVD compensation
Coupling loss reduction
Effective pulse delay ~ ns in sub-mm devices
1/2/2019
Jana Jagerska, IPEQ-LOEQ

13. Measurement techniques
Time resolved SNOM
M. L. M. Balistreri, H. Gersen et al., Science 294 (2001) p. 1080
1/2/2019
Jana Jagerska, IPEQ-LOEQ

14. Measurement techniques
Transmission resonances: Attenuated Total Reflection:
M. Galli et al., J. Sel. Areas in Communications 23,1402, (2005)
Y.A. Vlasov et al., “Active control of slow light on a chip with photonic crystal waveguides”, Nature 438, pp.65-68, 2005.
1/2/2019
Jana Jagerska, IPEQ-LOEQ

15. Thank you for your attention.
Information Sources
T. F. Krauss, J. Phys. D 40, 2666, (2005)
T. Baba, D. Mori, J. Phys. D 40, 2659, (2005)
Vlasov et al., Nature 438, 65, (2005)
Notomi et al., PRL 87, , (2001) …
Thank you for your attention.
1/2/2019
Jana Jagerska, IPEQ-LOEQ