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High-Speed Photodiode + Electrical Spectrum Analyzer
$10,500 total (PD + ESA, both new, all ships within 1–3 weeks) MEDIUM ● Required for RF-domain characterization; optical-domain tests (OSA) can proceed without itRole in QLT Fabrication
The photodiode + ESA pair provides RF-domain characterization that complements the optical-domain measurements of the OSA. While the OSA resolves spectral peaks, the PD+ESA detects beat frequencies, modulation responses, and noise properties that are invisible in the optical spectrum.
Process Integration
| Fab Step | PD+ESA Measurement | Pass/Fail Criteria |
|---|---|---|
| D2: Heater thermal response | Modulation bandwidth from electrical drive → optical response | -3 dB bandwidth > 10 kHz |
| D3: Laser RIN characterization | Intensity noise spectrum of CW sources | RIN < -130 dB/Hz |
| D4: FWM beat-note detection | RF beat between pump and signal confirms FWM interaction | Clear beat tone at expected frequency |
| D4: Rep rate verification | Mode-locked laser repetition rate on ESA | 100 MHz ± 1 ppm |
| D4: SPAD timing reference | PD provides trigger/timing reference for coincidence measurements | Jitter < 100 ps |
Instrument Chain
Signal flow: Tunable laser (#11) or MLL (#12) → optical signal through chip → PD (DET08CFC) → SMA cable → ESA (RSA5065N)
- PD converts photons to current; ESA displays frequency content of the photocurrent
- For FWM beat-note detection: the beat frequency equals the pump-signal detuning in optical frequency
Technical Specifications
| Test | Setup | PD Bandwidth Needed | ESA Span | What We Measure |
|---|---|---|---|---|
| FWM beat-note | MLL pump + CW signal → chip → PD → ESA | 5 GHz | 0–5 GHz | Beat frequency between pump and signal; confirms FWM |
| Heater thermal response | Modulated heater voltage → chip → PD → ESA | 100 kHz | 0–100 kHz | Heater -3 dB bandwidth (target: > 10 kHz) |
| Heater step response | Step voltage → chip → PD → oscilloscope | 100 kHz | Time domain | Rise/fall time of thermo-optic response |
| Laser RIN | CW laser → PD → ESA | 5 GHz | DC–5 GHz | Relative intensity noise floor (< -130 dB/Hz) |
| MZI modulation depth | Modulated signal → PD → ESA | 1 GHz | 0–1 GHz | Electro-optic bandwidth of MZI (if applicable) |
| SPAD timing jitter | SPAD pulse → TDC (#20) + trigger from PD | 5 GHz | N/A (TDC mode) | Timing reference for SPAD coincidence |
| Parameter | Specification |
|---|---|
| Manufacturer | Thorlabs Inc. |
| Model | DET08CFC |
| Detector material | InGaAs (Indium Gallium Arsenide) |
| Wavelength range | 800–1700 nm |
| Bandwidth (−3 dB) | 5 GHz |
| Rise time | 70 ps (typical) |
| Fall time | 110 ps (typical) |
| Active area | 0.04 mm² |
| Responsivity | 1.0 A/W @ 1550 nm |
| Dark current | 1.5 nA (typical) |
| NEP | 2.4 × 10⁻¹⁵ W/√Hz |
| Junction capacitance | 0.3 pF |
| Bias voltage | -5 V (internal bias tee) |
| Max input power | 2 mW (CW, damage threshold) |
| Input connector | FC/PC (compatible with FC/APC cables) |
| Output connector | SMA (50 Ω) |
| Operating temperature | 0–40°C |
| No external power supply needed | ✅ (internally biased from signal) |
| Dimensions | 22 mm diameter × 57 mm length |
| Weight | < 50 g |
| Price | ~$430 |
| Parameter | Specification |
|---|---|
| Manufacturer | Rigol Technologies |
| Model | RSA5065N |
| Type | Real-time spectrum analyzer with tracking generator + VNA |
| Frequency range | 9 kHz – 6.5 GHz |
| DANL | < -165 dBm (typical, with preamp) |
| Phase noise | < -108 dBc/Hz @ 10 kHz offset (typical) |
| Minimum RBW | 1 Hz |
| Real-time bandwidth | 25 MHz (standard); 40 MHz (with option) |
| Tracking generator | Built-in (output: -20 to 0 dBm) |
| VNA mode | Built-in (S11, S21; requires calibration kit) |
| Display | 10.1" capacitive multi-touch (1024 × 600) |
| Interface | USB (host + device), LAN (Ethernet), HDMI, GP-IB (optional) |
| Power input | 100–240 VAC, 50/60 Hz, max 95 W |
| Dimensions | 410 mm × 224 mm × 135 mm |
| Weight | 4.95 kg (10.9 lbs) |
| Operating temperature | 0–50°C |
| Component | Alternative | Key Spec | Price (New) | Notes |
|---|---|---|---|---|
| PD | Thorlabs DET025AFC (2.5 GHz) | Lower BW; adequate for heater test | ~$280 | Budget option |
| PD | Thorlabs DET08CFC (5 GHz) | Our pick ● best value at 5 GHz | ~$430 | |
| PD | Discovery Semi DSC40S (40 GHz) | Ultra-high BW; balanced detection | ~$2,000 | Overkill for our tests |
| PD | Thorlabs DXM30AF (30 GHz) | Module format; high BW | ~$3,500 | For future high-speed tests |
| ESA | Siglent SSA3032X Plus (3.2 GHz) | Budget; good for heater tests | ~$3,000 | 3.2 GHz may limit FWM detection |
| ESA | Rigol RSA5065N (6.5 GHz) | Our pick ● best value, real-time | ~$9,000–$12,000 | |
| ESA | Rigol DSA875 (7.5 GHz, swept only) | Cheaper; no real-time mode | ~$8,500 | Less capability |
| ESA | Keysight N9000B CXA (3.6–26.5 GHz) | Industry standard; modular | $15,000–$40,000 | Premium; future-proof |
| ESA | R&S FPC1500 (5 GHz) | Budget; Rohde & Schwarz quality | ~$5,000 | Good entry option |
Vendor Options & Pricing
| Component | Part Number | Quantity | Unit Price | Total |
|---|---|---|---|---|
| DET08CFC InGaAs PD (5 GHz) | DET08CFC | 1 | $430 | $430 |
| SMA-SMA cable (1 m, 50 Ω) | CA2818 | 2 | $25 | $50 |
| BNC-SMA adapter | Various | 2 | $10 | $20 |
| Rigol RSA5065N ESA | RSA5065N | 1 | $10,000 | $10,000 |
| N-SMA adapter (ESA input) | ● | 1 | $15 | $15 |
| Total system | $10,515 |
Used/Refurbished Market
| Item | Used Price | Notes |
|---|---|---|
| Rigol RSA5065 (non-N model) | $5,000–$8,000 | Without tracking gen |
| Keysight N9000A CXA | $5,000–$15,000 | Older model; excellent specs |
| Agilent E4402B | $2,000–$5,000 | Classic ESA; 3 GHz |
| HP 8594E | $1,000–$3,000 | Ancient but functional; 2.9 GHz |
Our Budget Recommendation
NEW PURCHASE (fastest delivery):
- DET08CFC: $430 ● ships next-day from Thorlabs ⚡
- Rigol RSA5065N: $10,000 ● lead time 1–3 weeks from Newark, Rigol direct, or TEquipment
- Many distributors stock Rigol instruments and ship same-week
Budget: $10,500 total (PD + ESA, both new, all ships within 1–3 weeks)