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Photonic Integrated Circuits in NASA Astrophysics Technology

Created: 2026-04-07 (session 69)

Summary

NASA is funding three parallel photonic integrated circuit (PIC) tracks for HWO-era astrophysics: (1) an AWG+MKID cryogenic spectrometer for high-dispersion coronagraphy (TRL 4, stalled), (2) a Si3N4 AWG+RDL spectrometer for precision radial velocity (TRL 3, active SBIR), and (3) a PIC-based coronagraph that replaces bulk optics entirely (TRL 2, active ECI/ARC). All three are in the TRL 2-4 range with none yet reaching the TRL 5 threshold for mission-level consideration. The AstroPIC coronagraph track is the most architecturally novel: it would eliminate the traditional coronagraph entirely.

Why PICs for Astrophysics

Traditional astrophysics instruments — spectrographs, coronagraphs — use bulk optics: prisms, gratings, mirrors, waveplates. These are heavy, large, and sensitive to thermal/mechanical disturbances. Photonic integrated circuits process light on a chip (typically Si3N4/SiO2 or silicon photonics), offering: - 100-1000x size reduction (chip vs benchtop instrument) - Single-photon capability when integrated with superconducting detectors (MKID, SNSPD) - Programmability: PIC circuits can be reconfigured electronically - Mass/power/cost reduction: critical for HWO mass budget

The challenge: space-grade PIC fabrication, coupling efficiency, thermal management, and scaling to the wavelength ranges and resolving powers needed for exoplanet characterization.

Three Parallel Tracks

Track 1: AWG+MKID — Cryogenic High-Dispersion Coronagraphy (HDC)

Status: TRL 4 achieved, stalled. No active follow-on in TechPort.

Project ID Program Period TRL Status
AWG+MKID Phase I 102233 SBIR 2020 2→4 Closed_Out
AWG+MKID Phase II 113265 SBIR 2023 3→4 Closed_Out
  • Company: Ultra-Low Loss Technologies, Goleta CA. PI: Renan Moreira.
  • Application: High Dispersion Coronagraphy (HDC) — the technique that combines coronagraphic star suppression with high-resolution spectroscopy to distinguish planetary atmosphere lines from stellar residuals. Essential for HWO exo-Earth characterization.
  • Technology: Arrayed waveguide grating (AWG) photonic chip integrated with Microwave Kinetic Inductance Detector (MKID) superconducting detector array. Wavelength range 0.4-2.0 µm (full HWO visible/near-IR). 60% system QE fiber-to-MKID. PIC < 4 cm². ~100 mK operating temp. 100-1000 MKIDs, internal Q ≥ 100,000.
  • Phase II deliverable (fileId 378899, read session 68): Monolithic on-chip cryogenic spectrometer prototype. HR-AWG microscopy (5-channel output), MKID-SNS waveguide-inductor integration schematic, gold chip package.
  • Pipeline stall: Phase II reached TRL 4 in 2023. No SAT, CT4LT, or SBIR Phase III visible in TechPort. If HWO requires HDC as a planet characterization technique, a TRL 4→7 bridge program is needed. The ~2027-2030 window is critical if this technology is to feed HWO instrument development.

Hardware image: See assets/awg-mkid-phase2-hardware.png (from session 68).

Track 2: AWG+RDL — Si3N4 High-Resolution Spectrometer for PRV

Status: TRL 3, active SBIR Phase II through mid-2026.

Project ID Program Period TRL Status
RDL-AWG Phase I 154735 SBIR 2023-2024 3→5 Completed
RDL-AWG Phase II 158704 SBIR 2024-2026 3→5 Active
  • Company: New Integration Photonics Inc., Chevy Chase MD. PI: Wei-lun Hsu. JPL co-org.
  • Application: Precision Radial Velocity (PRV) — the indirect Doppler method for exoplanet detection and mass characterization. Complementary to direct imaging; provides masses for HWO candidates.
  • Technology: Reusable Delay Line AWG (RDL-AWG) on Si3N4/SiO2. The RDL innovation replaces the large waveguide array in traditional AWGs with a single recirculating delay line, reducing footprint by ~1000x. Resolving power R > 150,000 within 20 nm bandwidth. >70% throughput. Form factor <20 cm³ (vs competitors ~200 cm³). Integration with 1D InGaAs CCD array.
  • Schematic: (from NIP briefing chart fileId 317301, session 69): Telescope → single-mode fibers → photonic lantern → MMI splitter + reference input → directional couplers → FPR → CCD.
  • Phase II deliverables: Single-stage RDL-AWG at R=150,000, cascaded two-stage design with flat-top spectrum, parabolic taper design, 1D CCD integration in butterfly package.
  • Note: RDL-AWG is architecturally different from AWG+MKID (Track 1). Track 1 couples to cryogenic MKID detectors (need for extreme sensitivity), Track 2 uses room-temperature InGaAs CCD. Track 1 targets spectroscopy of coronagraphy output; Track 2 targets PRV detection of Doppler shifts.

Track 3: AstroPIC — PIC Coronagraph (Replaces Bulk Optics)

Status: TRL 2, active ECI/ARC through June 2026. Most architecturally novel.

Project ID Program Period TRL Status
AstroPIC 154861 ECI 2023-2026 1→2 Active
  • PI: Dan Sirbu, Ames Research Center (also Co-I on Belikov MSWC SAT [96374]).
  • Collaborators: Stanford, JPL, GSFC, STScI, Caltech, U. Arizona — broadest institutional base of any PIC astrophysics project.
  • Application: High-contrast imaging and spectral characterization of exoplanets for HWO. The chip replaces the coronagraph (not just the spectrograph).
  • Technology: PIC decomposes wavefronts into constituent modes using photonic circuits. By separating starlight (coherent, single spatial mode) from planet light (incoherent, unresolved), AstroPIC can suppress stellar residuals more efficiently than bulk-optics coronagraphs. The chip is "universal" and can be reprogrammed electronically to optimize for each target star.
  • Performance claims: 100x lighter, 30x smaller than traditional coronagraph. Would relax HWO requirements and increase science margins.
  • Hardware: Two AstroPIC chips under microscope (fileId 389580, session 69). Each chip is ~2 cm elongated, showing dense waveguide routing: fiber coupler pads on left, complex photonic logic (splitter trees, delay lines, phase shifters, directional couplers) extending right. See:

AstroPIC chips under microscope

  • TRL 2 = proof-of-concept: The chip has been fabricated and demonstrates basic mode-sorting function. TRL 3 (component-level) would require demonstrating the coronagraphic function in a controlled environment.
  • Program context: ECI (Early Career Initiative) is STMD funding, but AstroPIC targets SMD/APD science. Same ECI program umbrella as RDRE [154860] rocket combustion — broad early-career technology mandate.

Comparison Across Tracks

Parameter AWG+MKID (T1) RDL-AWG (T2) AstroPIC (T3)
Function Spectrometer (HDC) Spectrometer (PRV) Coronagraph
Platform Si-based + MKID Si3N4/SiO2 Custom PIC
Detector MKID (cryogenic, ~100mK) InGaAs CCD (room temp) Traditional camera
Resolving power Very high (HDC R > 100k) R > 150,000 N/A (coronagraph)
TRL (as of Apr 2026) 4 (stalled) 3 (active) 2 (active)
HWO relevance Exo-Earth spectroscopy Planet mass determination Primary star suppression
Key risk MKID integration at scale R and throughput simultaneously Modal wavefront control in space

Pipeline Gap Assessment

All three tracks are below TRL 5. For HWO (target ~2040s launch): - Track 1 (AWG+MKID): TRL 4, needs ~TRL 6-7 for mission consideration. No current funding. Most time-critical if HDC is baselined for HWO instrument 2. - Track 2 (RDL-AWG): TRL 3, SBIR Phase II active. If Phase II achieves TRL 5, a Phase III or SAT grant could bridge to mission-level. More mature commercial ecosystem (PRV spectrographs have ground-based analogs). - Track 3 (AstroPIC): TRL 2, most disruptive but most immature. A PIC coronagraph at TRL 7 would be transformative for HWO instrument mass budget, but the path from TRL 2→7 is a decade-scale effort.

The HWO PIC technology gap: None of the three tracks has a CT4LT or SAT-level investment. CT4LT [183303-183305] (Northrop/LM/BAE) does not appear to target PIC technology — it focuses on system-level observatory architecture. PIC instruments represent an emerging alternative architecture that could reduce HWO instrument complexity, but current TechPort investment is at the SBIR/ECI level (TRL 2-4), not the CT4LT level (TRL 5-7).