Scalable Frequency Generation from Single Optical Wave

(1)

Scalable Frequency Generation from

Single Optical Wave

S. Radic

Jacobs School Of Engineering

Qualcomm Institute

(2)

- Motivation

- Bandwidth Engineering

- Noise Inhibition and Coherency Limit

- Spectral Shaping

- Implications:

- Optical

(3)

AW

G

RX

1

2

3 N

2xN

N Channels

RX

AW

G

RX

1

2

3 N

(4)

Physical Parameter

_ITLA

_F-Generation

Spectral Coverage (nm)

₇₄

?

Power (dBm)

_7-15.5

?

RIN (dBc/Hz)

_-145

?

OSNR

_{0.1 nm}

(dB)

_>50

?

f (MHz)

_0.1

?

F-stability (GHz)

_{±1.5 (±3.0)}

?

Power Dissipation (W)

_3.5-7.0

_?

Carrier Generation

(5)

Conventional LD Array

f

Frequency Comb

dBm-level Optical Power OSNR > 40 dB

Multi-band Wavelength Range

MHz Linewidth

Individual Frequency Tracking Required kW/MW-level Power Dissipation

Output Power? OSNR?

Emission Bandwidth and Spacing? Linewidth?

Frequency Grid Locked

Watt-scale Power Dissipation

LD/TEC

(6)

• _{Mode-Locked Lasers}

- Cavity-defined

- Fixed grid,



f, bandwidth limits

- Low harmonic power

- Excess noise

• E/O Modulation

- Grid limited by RF generator

- Noise defined by front loss

• _{Resonant Generation}

-

Noise, Power

 P ~f-1 t PM AM f1 PM AM f2 f3 f4

(7)

f f₀ f₀+ Ideal Lasers (Narrow Linewidth)

Mixer

f f₀ f₀+ f₀+2 f₀+3 f₀+n

Advantage: No cavity

 freely tunable.

Disadvantage: No cavity means no inhibition mechanism.

- Noise introduced and grown by mixer.

(8)

Mixer efficiency



- ratio of newly created and input photons:

Figure Of Merit (FOM)

2 ~

e



PL



Kerr Index (n₂) W-1_m-1 Effective Waveguide Area (Aeff) m2 Nonlinearity (=2n2/Aeff) Loss dB/m Effective Length (m) FOM PL) Silicon Waveguide Silica Waveguide 2.1×10-18 3.2×10-20 8.3 0.035 0.6 8 500 0.00035 0.03 >1000 0.5 70 Mixer Platform

(9)

Pulsed vs. Continuous-Wave Generation

CW-seeding is low power  Requires higher mixing efficiency

f f

P

_CW

Mixer

Two-Tone CW

t

Mixer

f

P

_ML

Mode-Locked Seed

(10)

CW-Seeded Frequency Generation Efficiency

t ω Dispersion-less Nonlinear Medium _t ω

Efficiency Limit set by SBS Threshold

21 _eff SBS B A P g L  2 1 42 1 SBS SBS B k P L n g    _ _   _ _   0.14 1

_ _ for ordinary silica fiber

2.81 1

_ _ for SBS-suppressed mixer

Modified Carson’s Rule for HPM

0 10 20 30 40 50 0 10 20 30 40 50 60

Phase rotation parameter m

T

one o

rder

k

Highest tone order

1

k_PL_

High-Count generation is prohibited

in homogeneous mixers

(11)

Higher-order mixing efficiency proportional to Peak Power P

_peak t ω Dispersion-less Nonlinear Medium _t ω Δω P_peak

(12)

Shock-Wave Mixer

t  t   Pulse Compression

Stage Mixing Stage

Nonlinear Section 1 Linear Section Nonlinear Section 2 t 

(13)

1450 1500 1550 1600 1650 -60 -50 -40 -30 -20 -10 0 Wavelength, nm Po w e r, d B m Fiber 6-2-6 200m Fiber 6-2-7 250m Fiber 6-2-8 250m

(14)

z

D(z), r(z)

~nm

1200 1300 1400 1500 1600 1700 1800 -2 -1.5 -1 -0.5 0 0.5 1 Wavelength, nm D is pers io n , ps /n m /k m

(15)

D_peak = 0.0 ps/nm/km D_peak = -0.2 ps/nm/km D_peak= -0.4 ps/nm/km

D_peak = 0.4 ps/nm/km

(16)

Beyond Stochastic Barrier

1520 1540 1560 1580 1600 1620 1640 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 Wavelength, nm D isp e rsi o n , p s /n m /k m

Standard

Synthetic

(17)

Stochastic Barrier

1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 1800 -70 -60 -50 -40 -30 -20 -10

Before Synthesis

1400 1450 1500 1550 1600 1650 1700 -70 -60 -50 -40 -30 -20 -10 Walelength, nm Po w e r, d B m

After Synthesis

(18)

-40 -20 0 1500 1520 1540 1560 1580 1600 1620 •Wavelength (nm) • Relative P ower (dB) -70 -60 -50 -40 -30 -20 -10 0 10 1590 1592 1594 1596 1598 1600

(19)

- Motivation

- Bandwidth Engineering

- Noise Inhibition and Coherency Limit

- Spectral Shaping

- Implications:

- Optical

(20)

Noise Origins

Mixer

Excess Mixer Noise

(21)

Mixer Linewidth  f f0 f0+ f f₀ f0+ f₀+2 f₀+3 f₀+n  2 3 n f f₀ f₀+ Ideal Lasers (Narrow Linewidth)

Finite Linewidth Laser ()

f

f₀ f₀+ f₀+2 f₀+3 f₀+n

Mixer

Finite-Linewidth Laser Seed

(22)

Phase-Referencing by Injection Locking

Master

Slave

• Weak, narrow master;

• Strong, broad slave;

• Injection locking results in

strong, narrow oscillator.

(23)

-2 -1 0 1 2 0 0.2 0.4 0.6 0.8 1 Frequency (MHz) A m plit ude RIO C33 1st line 5th line 10th line 15th line 20th line 25th line 30th line

Spectral Fidelity

• Linewidth broadens quadratically

with comb tone order

• At low copy count there is also

the linear contribution to

linewidth scaling law

Span 5 MHz

0 10 20 30 40 0 500 1000 1500 2000 2500 Comb line L ine widt h F W HM ( k Hz

) Measurement_{2nd order polynomial fit}

Normalized

(24)

In Phase Quadrature In Phase Quadrature

ITLA

COMB

-40 -20 0 1500 1520 1540 1560 1580 1600 1620 •Wavelength (nm) • Relative P ower (dB)

Comb

(25)

- Motivation

- Bandwidth Engineering

- Noise Inhibition and Coherency Limit

- Spectral Shaping

- Implications:

- Optical

(26)

 Uses CW, rather than pulsed seed: achieves generation

efficiency by managed shock-wave formation.

 Tunable frequency grid: from

10 GHz

to >

400 GHz

.

 Requires precise intra-mixer waveform control.

Shock-Wave Parametric Mixer

Dispersive stage Nonlinear stage f f t t PM AM 2 Δf Nonlinear stage f Δf

Carrier Generation

(27)

f

Δf

 Pedestal pulses may form at high compression ratio



Introduces spectral power ripple…

 Regenerative stage reshapes pulses into ideal form

 Active loop improves extinction by >

100-times

Inter-stage Shock-wave Shaping

Dispersive element NOLM _Nonlinear element PM AM 2 t _P out P_in t Δf Δf f

Carrier Generation

(28)

Setup

AM 2 10 GHz -4 -2 0 2 4 0 0.5 1 Time [ps] Amplitude SMF₁ -4 -2 0 2 4 0 0.5 1 Time [ps] SMF₃ 185 190 195 200 205 -80 -70 -60 -50 -40 -30 Frequency [THz] HNLF PM 185 190 195 200 205 -80 -70 -60 -50 -40 -30 Frequency [THz] Power [dB] 0.4 THz 185 190 195 200 205 -80 -70 -60 -50 -40 -30 Frequency [THz] -4 -2 0 2 4 0 0.5 1 Time [ps] NOLM₁ 1 THz NOLM₂ 185 190 195 200 205 -80 -70 -60 -50 -40 -30 Frequency [THz] 2 THz -4 -2 0 2 4 0 0.5 1 Time [ps] SMF₂

(29)

Very Dense Carrier Plan (10 GHz)

195.95 196 196.05 -60 -40 -20 0 Frequency [THz] 192.92 192.96 193 -60 -40 -20 0 Frequency [THz] P o w e r [dB] 194.95 195 195.05 -60 -40 -20 0 Frequency [THz] <2 dB 1460 1500 1540 1580 1620 -80 -70 -60 -50 -40 -30 Wavelength [nm] Po w e r [ d B ]

>1500 lines

Carrier Generation

(30)

- Motivation

- Bandwidth Engineering

- Noise Inhibition and Coherency Limit

- Spectral Shaping

- Implications:

- Optical

(31)

(32)

189

191

193

195

197

0

2

6

10

14

18 Frequency (THz)

NF (dB)

PS-Multicasting PI-Multicasting 5.6 dB NF Improvement 3-dB Quantum Limit

“Isotropic” Mixer

(33)

-42 -40 -38 -36 -34 -32 -30 -10 -9 -8 -7 -6 -5 -4 Input Power [dBm] log (BER)

Scalable Frequency Generation from Single Optical Wave