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 Laboratories Support: NSF, ARO, Intel 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 PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Proposed Optical Rep-rate Multiplier Input: Output: high-rate very high-rate pulse train pulse train Optical Rep-Rate Multiplier T T/N • Conversion of a modelocked source (e.g., 10 GHz) to a much higher rate (e.g, 100 GHz – 1 THz) 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 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) 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 Shaped Mask output 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) 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 Data burst packet -30 -20 -10 0 10 20 30 -30 -20 -10 0 10 20 30 Time (ps) Time (ps) •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) PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Generalized Spectrometer DST pulse shaper output spectra 1.5 Periodic burst of pulses 1 Power (a.u.) 0.5 0 4 2 830 835 840 845 850 855 860 865 0 Output Slit (mm) -2 Wavelength (nm) -4 • 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) PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Multiple Wavelength-Shifted Pulse Bursts Periodic burst Data packet Pulse shaping slit position: -1 mm +1 mm -30 -20 -10 0 10 20 30 -30 -20 -10 0 10 20 30 Time (ps) Time (ps) Intensity profile is unchanged as wavelength is varied! 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 PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Bulk DST / Integrated AWG Analogy Slit d 1 f Mask Output Input Focus Grating/lens Patterned input frequency Output beam formation d 1 = 0 components slit(s) Fsec read-out of an integrated arrayed waveguide grating leads to pulse sequence generation similar to that obtained with DST pulse shaper 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 200 fs input pulses at 50 MHz free spectral range (FSR) Semi-log plot Ch1 Ch4 Expanded view Source laser 1556 1558 1560 1562 1564 1520 1540 1560 1580 1600 Wavelength (nm) Wavelength (nm) • 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) 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 40 GHz 100 GHz channel spacing channel spacing Channel 3 -15 -10 -5 0 5 10 15 -30 -20 -10 0 10 20 30 100 GHz 40 GHz channel spacing channel spacing Channel 4 -30 -20 -10 0 10 20 30 -15 -10 -5 0 5 10 15 Time (ps) Time (ps) Leaird, Shen, Weiner, Sugita, Kamei, Ishii, and Okamoto, IEEE Photon. Tech. Lett. 13 , 221 (2001) 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 on guide-by-guide basis Waveguide array Spatial Output profile of waveguide slab excitation Input slab Output pulse train Input guide PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Flat-topped AWG Design ‘Pulse’ AWG • Tailor loss profile on a guide-by- guide basis within the waveguide array • Demonstrates ‘one-guide, one- pulse’ methodology Loss profile • Standard AWGs w/ 40-GHz channel spacing loss-engineered to yield 19 (21) output pulses Output • Excess insertion loss: pulse 7 dB (7.5 dB) train Leaird, Weiner, Kamei, Ishii, Sugita, and Okamoto, IEEE Photon. Tech. Lett. 14 , 816 (2002) PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Output Power Spectra Module 1 0 out 1 out 2 out 3 -10 out 4 Transmittance [dB] -20 -30 -40 -50 1555.0 1557.5 1560.0 1562.5 1565.0 Wavelength [nm] • 40 GHz channel spacing, 500 GHz FSR • Sinc-like spectra consistent with flat-topped pulse train design 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) PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
Femtosecond read-out in double-pass operation 1 – 2 ps Λ 1 Short Λ 2 pulse laser Λ 3 Either standard or loss-engineered AWG Λ 4 Measurement • 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, …) 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 Data: Measured cross-correlation -50 -40 -30 -20 -10 0 10 20 30 40 50 Theory: Calculated by auto-convolving the single-pass temporal response -50 -40 -30 -20 -10 0 10 20 30 40 50 Time (ps) • 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. PURDUE UNIVERSITY ULTRAFAST OPTICS & OPTICAL FIBER COMMUNICATIONS LABORATORY Integrated Photonics Research Conference, invited talk, Vancouver (July, 2002)
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