Very High Speed Pulse Sequence Generation via Femtosecond Read-out - - PowerPoint PPT Presentation

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Very High Speed Pulse Sequence Generation via Femtosecond Read-out - - PowerPoint PPT Presentation

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Very High Speed Pulse Sequence Generation via Femtosecond Read-out of Arrayed Waveguide Gratings A.M. Weiner, D.E. Leaird Purdue University K. Okamoto 1 , S. Kamei 2 , M. Ishii 2 , and A. Sugita 1 1 NTT Electronics Corporation 2 NTT Photonics

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SLIDE 1

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Very High Speed Pulse Sequence Generation via Femtosecond Read-out

  • f Arrayed Waveguide Gratings

A.M. Weiner, D.E. Leaird

Purdue University

  • K. Okamoto1, S. Kamei2, M. Ishii2, and A. Sugita1

1 NTT Electronics Corporation 2 NTT Photonics Laboratories

Support: NSF, ARO, Intel

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SLIDE 2

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Proposed Ultrafast Parallel-to-Serial Converter

Optical Word Generator

  • Goal: an optical system that directly maps parallel, spatial input

information into a serial, ultrafast optical output signal

  • Application: Optical TDM transmission of parallel electronic data words
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SLIDE 3

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Proposed Optical Rep-rate Multiplier

Output: very high-rate pulse train Input: high-rate pulse train T T/N Optical Rep-Rate Multiplier

  • Conversion of a modelocked source (e.g., 10 GHz) to a much higher rate

(e.g, 100 GHz – 1 THz)

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SLIDE 4

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Outline

  • Bulk optic pulse shapers
  • Femtosecond read-out of an AWG
  • Loss-engineered AWG for flat-topped pulse train generation
  • Double-pass AWG operation for fs pulse train multiplexing
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SLIDE 5

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Fourier Transform Pulse Shaping

A.M. Weiner, Rev. Sci. Instr. 71, 1929 (2000)

  • Fourier synthesis via parallel spatial/spectral modulation
  • Numerous spatial masking technologies: liquid crystal arrays, MEMS arrays …
  • Diverse applications: fiber communications, coherent quantum control...
  • Partial integration demonstrated using double-pass AWG

e.g., Takenouchi, Goh, and Ishii, Electron. Lett. 37, 777 (2001)

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SLIDE 6

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Direct Space-to-Time Pulse Shaper

Femtosecond Response of a Generalized Spectrometer

Slit f f Mask Shaped

  • utput

Fs input

Pulse tilt

  • Output temporal profile is directly scaled version of input mask
  • Replacing spatial mask with optoelectronic modulatory array will

lead to parallel electronic to serial optical conversion at Gframe/s

  • Spectrum can be shifted via transverse position of slit

without affecting intensity profile

  • Chirp may be set to zero or tuned via longitudinal position of slit

Leaird and Weiner, IEEE JQE 37, 494 (2001)

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SLIDE 7

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Direct space-to-time pulse shaper data

850 nm

Periodic burst Data packet

Time (ps)

  • 30
  • 20
  • 10

10 20 30

Time (ps)

  • 30
  • 20
  • 10

10 20 30

  • Temporal data is directly scaled version of a fixed spatial mask
  • Gaussian beam profile leads to temporal roll-off

Leaird and Weiner, IEEE JQE 37, 494 (2001)

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SLIDE 8

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Generalized Spectrometer

1.5 830 835 840 845 850 855 860 865

  • 4
  • 2

2 4 0.5 1

Wavelength (nm) Output Slit (mm) Power (a.u.)

DST pulse shaper output spectra

Periodic burst of pulses

  • A spectrometer with highly structured, user defined spectral passbands
  • Can be scanned as in a conventional spectrometer

Leaird and Weiner, IEEE JQE 37, 494 (2001)

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SLIDE 9

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Multiple Wavelength-Shifted Pulse Bursts

Time (ps)

  • 30
  • 20
  • 10

10 20 30

Time (ps)

  • 30
  • 20
  • 10

10 20 30

Pulse shaping slit position:

  • 1 mm

+1 mm

Periodic burst Data packet

Intensity profile is unchanged as wavelength is varied!

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SLIDE 10

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Bulk Optics and Integrated Optic Direct Space-to-Time Pulse Shapers

Bulk optics AWG

U.S. Quarter

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SLIDE 11

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Mask Slit Output d1 f Input Patterned input beam formation Grating/lens

d1 = 0

Focus frequency components Output slit(s) Bulk DST / Integrated AWG Analogy

Fsec read-out of an integrated arrayed waveguide grating leads to pulse sequence generation similar to that obtained with DST pulse shaper

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SLIDE 12

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Femtosecond Readout of an AWG: Output Power Spectra

Wavelength (nm)

1520 1540 1560 1580 1600 Ch1 Ch4 Source laser

Wavelength (nm)

1556 1558 1560 1562 1564

Semi-log plot Expanded view free spectral range (FSR)

200 fs input pulses at 50 MHz

  • The AWG functions as a periodic narrow-band filter.
  • In normal WDM applications, the FSR exceeds the overall optical bandwidth.
  • For our femtosecond readout, the optical bandwidth exceeds the FSR.

Leaird, Shen, Weiner, Sugita, Kamei, Ishii, and Okamoto, IEEE Photon. Tech. Lett. 13, 221 (2001)

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SLIDE 13

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

1-THz Pulse Sequences

Standard AWGs, 1 ps delay increment Input: 200 fs, 50 MHz

  • 30
  • 20
  • 10

10 20 30

Time (ps)

  • 30
  • 20
  • 10

10 20 30

Time (ps)

  • 15
  • 10
  • 5

5 10 15 100 GHz channel spacing Channel 4

  • 15
  • 10
  • 5

5 10 15 Channel 3 40 GHz channel spacing 100 GHz channel spacing 40 GHz channel spacing Leaird, Shen, Weiner, Sugita, Kamei, Ishii, and Okamoto, IEEE Photon. Tech. Lett. 13, 221 (2001)

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SLIDE 14

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

One Guide – One Pulse

  • Pulses temporally separated by the delay increment per guide

(= FSR-1).

Temporal profile

  • n guide-by-guide

basis Spatial profile of waveguide excitation Output pulse train

Waveguide array Input guide Input slab Output slab

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SLIDE 15

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Flat-topped AWG Design

  • Tailor loss profile on a guide-by-

guide basis within the waveguide array

  • Demonstrates ‘one-guide, one-

pulse’ methodology

  • Standard AWGs w/ 40-GHz

channel spacing loss-engineered to yield 19 (21) output pulses

  • Excess insertion loss:

7 dB (7.5 dB)

‘Pulse’ AWG Loss profile Output pulse train

Leaird, Weiner, Kamei, Ishii, Sugita, and Okamoto, IEEE Photon. Tech. Lett. 14, 816 (2002)

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SLIDE 16

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Output Power Spectra

Module 1

  • 50
  • 40
  • 30
  • 20
  • 10

1555.0 1557.5 1560.0 1562.5 1565.0 Wavelength [nm] Transmittance [dB]

  • ut 1
  • ut 2
  • ut 3
  • ut 4
  • 40 GHz channel spacing, 500 GHz FSR
  • Sinc-like spectra consistent with flat-topped pulse train design
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SLIDE 17

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

500-GHz Flattened Pulse Sequences

21 guide loss-engineered AWG, 2 ps delay increment

Leaird, Weiner, Kamei, Ishii, Sugita, and Okamoto, IEEE Photon. Tech. Lett. 14, 816 (2002)

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SLIDE 18

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Femtosecond read-out in double-pass operation

  • Single-pass: single input pulse generates identical, slightly wavelength shifted,

high rate pulse bursts at each of N output channels (1/N energy per output)

  • Double-pass: recombines energy onto a single fiber

– Circumvents power loss. – Provides flexibility to separately control each channel (delay, intensity, …) Short pulse laser Measurement

Λ1 Λ2 Λ3 Λ4

1 – 2 ps

Either standard or loss-engineered AWG

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SLIDE 19

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Double-Pass Temporal Response – Single Channel

19 pulse loss-engineered AWG, 500 GHz FSR

  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50

Time (ps)

  • 50
  • 40
  • 30
  • 20
  • 10

10 20 30 40 50

Measured cross-correlation Calculated by auto-convolving the single-pass temporal response

Data: Theory:

  • Each pulse generated in single-pass generates a full burst upon double-pass
  • Overall double-pass response = autoconvolution of single-pulse response:

Square burst converted into a triangle!

Leaird, Weiner, Kamei, Ishii, Sugita, and Okamoto, IEEE Photon. Tech. Lett, in press.

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SLIDE 20

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Double Pass Output Spectra

19-pulse loss-engineered AWG, 4 free-space sections,

Wavelength (nm)

1554 1556 1558 1560 1562 1564 1566

Power (dBm)

  • 90
  • 80
  • 70
  • 60
  • 50

FSR Λ1 Λ2 Λ3 Λ4 Λ1 Λ2 Λ3 Λ4 Λ1 Λ2 Λ3 Λ4

The four wavelength combs, corresponding to the four free- space channels, are successfully recombined.

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SLIDE 21

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Multiple Channel Temporal Response

100 200 300 400 500 600 700

Time (ps)

100 200 300 400 500 600 700 Λ1 Λ2 Λ4 Λ1 Λ2 Λ4 − advanced

Time (ps)

100 200 300 400 500 600 700 Λ1 Λ2 Λ4 blocked

Substructure not resolved within each burst

  • Pulse bursts observed with a 50 GHz photodiode and sampling scope.
  • Individual bursts controlled (delay, on/off) via ‘output’ free-space sections.

Leaird, Weiner, Kamei, Ishii, Sugita, and Okamoto, IEEE Photon. Tech. Lett., in press.

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SLIDE 22

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Pulse Burst Processing

Intensity cross-correlations fully resolve temporal features.

Time (ps)

  • 100
  • 50

50 100

Λ1 Λ4 Λ2 Λ3

4 free-space sections 1 free-space section blocked

Over 100 pulses on a single output fiber!

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SLIDE 23

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

AWG Double-Pass Pulse Sequence Generator

Scaling Laws

Number of pulses ~ FSR 2 f     δ  

δf = pass-band width # of pulses per channel

FSR f     δ  

# of channels

Single-pass loss ~ ηintrinsic + ηloss-eng + ηsplitting Double-pass loss ~ 2 (ηintrinsic + ηloss-eng )

f ~ FSR δ Applicable to AWGs either with or without loss-engineering

A single input pulse can be split into hundreds of pulses, with little or no fundamental excess loss!

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SLIDE 24

PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY

Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)

Summary

  • Exploiting the close analogy with direct space-to-time pulse

shapers, we have demonstrated new functionalities for AWGs in the area of time-domain pulse processing.

  • Potential for “time-domain beam splitters” generating long

pulse sequences with little or no fundamental loss.

  • Rich opportunities for further design optimizations and

innovations.