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Photonic Integrated Circuits (PICs)

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This course is offered each Fall semester by the Department of Electrical and Computer Engineering at Aarhus University as part of our Photonics Teaching Program.

Overview

Photonic integration is changing how light is generated, guided, and controlled on a chip, enabling faster communication, compact sensors, and emerging quantum technologies. This course takes you through that full journey.

We begin with the physics of light–matter interaction and semiconductor bandgaps, then move into device principles such as PN junctions, optical confinement, and laser dynamics. You will explore waveguides, amplifiers, and resonators, see how materials and fabrication shape performance, and extend these ideas to visible, mid-infrared, and deep-UV photonics.

Teaching combines lectures, problem-solving sessions, simulations, and live laboratory demonstrations. Guest lectures from researchers and engineers link classroom concepts to current photonics research and industry developments in Denmark and abroad.

By the end of the semester, you will have designed and analyzed your own photonic integrated circuit (PIC), connecting physical insight with practical device engineering.

Course information

Course content

The course follows the full chain of photonic integration, connecting the physics of light–matter interaction with the engineering of chip-scale optical systems. Topics include:

  1. Light generation, absorption, and emission in semiconductors
  2. PN junctions, carrier recombination, and population inversion
  3. Waveguides and optical fibers: confinement, polarization, and propagation loss
  4. Laser operation and dynamics: threshold, rate equations, modulation response, and relaxation oscillations
  5. Optical amplification, reflection, and feedback in cavities and resonators
  6. Material platforms and fabrication methods based on silicon and III–V semiconductors, including hybrid integration
  7. Packaging, thermal management, and reliability in photonic devices
  8. Advanced areas such as nonlinear optics, mid-infrared and deep-ultraviolet sources, and quantum photonic integration.

Teaching combines lectures, problem-solving sessions, simulations, and laboratory demonstrations. The course concludes with an individual design study that bridges physical insight and practical device engineering.

Purpose of the course

Photonic Integrated Circuits (PICs) bring the power of optics onto a chip, enabling technologies that define modern communications, sensing, and quantum systems. This course reveals how light is generated, guided, and controlled at the micro- and nanoscale, linking physical principles with real device engineering. Through lectures, simulations, and laboratory demonstrations, you will explore how materials, geometry, and fabrication shape performance, and apply this understanding in a design study where you conceive and analyze your own PIC.

Learning outcome

After completing the course, you will be able to:

  1. Explain the physics of light–matter interaction and the operation of key photonic devices, including light sources, modulators, amplifiers, and detectors
  2. Model the behavior of photonic devices and circuits using analytical and numerical methods, and interpret their performance metrics
  3. Describe fabrication approaches and material platforms for photonic integration, and discuss their respective advantages
  4. Identify and evaluate trade-offs among optical performance, scalability, efficiency, and packaging in integrated systems
  5. Apply this understanding in a design study that connects device-level physics with system-level applications in communications, sensing, and quantum technologies.

ECTS credits: 10

Prerequisites: Prior knowledge of electromagnetism and optics.

Program requirement: Active participation is mandatory.

Assessment: Oral exam is based on a written report centered on a design study incorporating one or more photonic devices. Grading follows the seven-point scale and includes an internal co-examiner.

Course coordinator: Nick Volet

Next edition

During the Fall semester: August – December, 2026.

Where and when?

📍 AU-ECE, Building 5125 (Edison), Finlandsgade 22

Lectures:
– Mondays 10:15–12:00, Room 417 or online via this Teams link
– Thursdays 12:15–14:00, Room 416 or online via this Teams link

Exercises and lab demos:
– Wednesdays 10:15–12:00, Room 120


Part 1

1. Light-matter interaction

Aug. 25 + Aug. 27 + Aug. 28 (week 35)
Course introduction and overview
Introduction to EMode Photonix
Two-level systems, absorption and spontaneous emission
Dispersion and scattering
Virtual states and nonlinear processes

→ Start survey: We’re excited to begin this semester with you! To help us better tailor the course to your needs and interests, we’d love to hear your expectations and any suggestions you may have. Your feedback is valuable, and the survey is completely anonymous. Please share your thoughts by clicking this link.


2. Bandgap to waveguides

Sept. 1 + Sept. 3 + Sept. 4 (week 36)
Bandgap and transparency (crystal vs amorphous)
Key semiconductor platforms (Si, GaAs, InP, silica)
Practical devices (InGaAs detectors, InP lasers, GaAs LEDs/solar cells)
Waveguides and optical fibers
Waveguides and optical fibers (modes, polarization, losses)
Power and units (dB, dBm)
Global context (submarine fiber networks)

  • SlidesPDF – PPT
  • Exercises: PDF
    • Design study preparation: PDF

3. On-chip light sources

Sept. 8 + Sept. 10 + Sept. 11 (week 37)
Incandescence (thermal emission) and luminescence
Stimulated emission
Laser principle: population inversion, threshold, and cavity feedback
Optical modes and coherence
Light-emitting diodes (LEDs), superluminescent diodes (SLDs), and laser diodes
Spectral properties: linewidth, free spectral range (FSR), and side-mode suppression ratio (SMSR)
Device structure and packaging, thermal management, and reliability

Semiconductor doping, and diode laser history
PN junction fundamentals, electron–hole recombination
I–V characteristics


4. Miniaturization and scalability

Sept. 15 + Sept. 17 + Sept. 18 (week 38)
Carrier and photon confinement
PIN junctions, and double heterostructures
Quantum wells and superlattices
Quantum cascade lasers
Quantum dots

Photonic crystals and structural color
Refractive index control and carrier effects
Kramers–Kronig relations
Nonlinear optics (Kerr effect)
Quantum tunneling and tunnel junctions
Vertical-cavity surface-emitting lasers (VCSELs): design and applications
Epitaxial growth and wafer-scale integration
III–V semiconductors and material foundations

Sept. 18 (Thursday): Deadline to submit group abstracts


5. Material platforms

Sept. 22 + Sept. 24 + Sept. 25 (week 39)

→ Sept. 22 (Monday): Feedback on submitted abstracts: PDF – PPT

Silicon, indium phosphide (InP), AlGaAs, InGaAsP, etc.
Wafer fabrication, lattice matching, bandgap engineering
Distributed Bragg reflectors (DBRs), phase shifts
Process Design Kit (PDK), Multi-Project Wafer (MPW), photonic integration

  • Slides: PDFPPT
  • Exercises: PDF Group work for projects

5B

Thin films and anti-reflective (AR) coatings. Distributed Bragg reflectors (DBRs). Corrugated waveguides. Fiber Bragg gratings (FBGs). Fabry-Perot interferometer and etalons.

  • BookletPDF
  • Slides: PDFPPT
  • Exercises: PDF
  • Solutions: TBC

6. Semiconductor growth and visible photonics

Sept. 29 + Oct. 1 + Oct. 2 (week 40)
Epitaxial growth: Molecular Beam Epitaxy (MBE) vs Metal-Organic Vapor Phase Epitaxy (MOVPE), lattice matching, strain and dislocations, quantum dots, wafer bonding, and heterogeneous integration

Blue laser diodes, GaN substrates, quantum wells, green gap, frequency doubling
Blu-ray technology, industrial applications, metal cutting

  • Solutions: TBC

7. Mid-infrared photonics

Oct. 6 + Oct. 8 (week 41)

→ Oct. 6 (Monday): Deadline to submit group reports

Greenhouse-gas absorption and atmospheric transmission; molecular absorption; HITRAN database; mid-IR light generation with quantum cascade lasers (QCLs) and difference-frequency generation (DFG); applications in gas sensing, free-space communication, and quantum frequency conversion.

→ Oct. 8 (Wednesday): Group presentations


Extra topics

Incoherence

Speckle effect. Superluminescent diodes (SLEDs) and their applications.
Optical coherence tomography (OCT): principles and uses.
Sagnac effect and modern optical gyroscopes.


Deep-UV photonics: Lasers, fibers and detectors. Nonlinear crystals and lithography


Pulses
Modulators. Side-band generation.
Modulation formats. Coherent communications.
Q-switching.
SESAMs: Semiconductor saturable absorber mirror.
Spiking and neuron networks


Steering
Scanners, optical phased arrays (OPAs).
Light detection and ranging (LIDAR).


Scattering
Brillouin effect and distributed optical sensing. 
Raman spectroscopy.


Narrow-linewidth lasers

Intrinsic linewidth and coherence length. 
Fiber lasers.
Optical feedback.
External-cavity diode lasers (ECDLs).

  • Slides: PDFPPT
  • Exercises: PDF
  • Solutions: TBC

Photodetection
Photodetectors.
Solar cells to ultrafast coherent receivers.
Mid-infrared detectors to solar-blind UV sensors.

Week 42 (Oct. 13 – 17): no teaching at AU.

Curious about Integrated Nonlinear Photonics?
Join us at EPFL (Lausanne, Switzerland) or online for a week. More info and registration (for free) at this link.

Part 2

8A. Recombination processes

Oct. 20 + Oct. 22 + Oct. 23 (week 43)
Dangling bonds and surface passivation. Band structure and direct/indirect bandgaps. Radiative and non-radiative recombination (Auger process). Phonons and momentum conservation. 

Oct. 22 (Wednesday): R-Day starts at 12:30 at the Clarke Building (5122-122).
R-Day is an open forum for students and researchers at ECE to meet, share ideas, and explore ongoing research activities. The event aims to inspire collaboration and raise awareness of the research taking place within the department.

8B. Laser performance

Confinement factors (transverse and longitudinal), comparison between edge-emitting lasers and VCSELs
Threshold conditions, longitudinal modes and free spectral range (FSR)
Rate equations for carrier and photon densities

  • Booklet: PDF
  • Slides: PDFPPT
  • Exercises: TBC

9. Dynamics

Oct. 27 + Oct. 29 + Oct. 30 (week 44)
Laser steady-state behavior, gain clamping, output power–current (LI) characteristics
Turn-on delay and small-signal modulation
Linearization of rate equations, transfer functions
Relaxation oscillations, bandwidth limits
Wavelength and material choices, packaging effects
Eye diagrams, and modern modulation formats (PAM-4)


10. Amplification and multiplexing

Nov. 3 + Nov. 5 + Nov. 6 (week 45)

Nov. 5 (Wednesday, 23:59): Deadline to submit individual abstracts

Infrared C-band: scattering, attenuation, and zero-dispersion point.
Erbium-doped fiber amplifiers (EDFAs). Arrayed waveguide gratings (AWGs).

→ Nov. 6 (Thursday, during class): Feedback on submitted abstracts


11. Semiconductor optical amplifiers

Nov. 10 + Nov. 12 + Nov. 13 (week 46)
Wavelength division multiplexing (WDM), coarse and dense WDM, and future integrated amplifiers.
Transverse confinement factor. Net gain and saturation.
Semiconductor optical amplifiers (SOAs). Small-signal gain factor.


12. Phase modulation

Nov. 17 + Nov. 19 + Nov. 20 (week 47)
Electro-optic effects. Pockels cells. Phase modulation using EO modulators (EOMs). Generation of optical sidebands. Material platforms: indium phosphide (InP), lithium niobate on insulator (LNOI). Applications in high-speed and quantum photonics.

Isolators and circulators.
Stabilization loop: Pound-Drever-Hall (PDH) method.


13.

Nov. 24 + Nov. 26 + Nov. 27 (week 48)

🎤 Nov. 24 (Monday) at 10:00:
Guest lecture by Søren Stobbe, Professor at DTU Electro, Founder and Chief Scientific Officer at Beamfox Technologies
"Subwavelength confinement of light in dielectrics"
Abstract: PDF

→ Course evaluation


14. Last session

Dec. 1 + Dec. 3+4 (week 49)
Course recap, exam prep, student project rehearsal, and future opportunities in photonics.
 

🎤 Dec. 1 (Monday) at 10:15:
Guest lecture by Peter Tønning, Senior System Engineer at UV Medico
"Far-UVC: current and future developments"

Dec. 3+4 (Wednesday+Thursday): Individual presentations (rehearsal)

Dec. 10 (Wednesday, 23:59): Deadline to submit final individual reports

Course evaluation

We hope you enjoyed this course, and we want to improve next semester.
Please take a few minutes to answer this Google survey (anonymous).

Thanks!
Nick, Asger, Jeppe, Lucas, and Pedro

Simulation exercises

We use EMode Photonix to simulate and analyze waveguide modes.

👉 Click here for instructions and resources to get started with EMode Photonix.

Re-exam: June 4 (Thursday, week 23)

Key dates:
– May 20 (Wednesday, week 21): deadline to submit your final report

Students wishing to be re-examined this semester must submit their abstract and report to Nick Volet by email before the above deadlines.

Exam and assessment: December 15–16 (week 51)

Assessment is based on an oral exam and a written report centered on a design study incorporating photonic integrated circuits.

Key dates:
November 5 (Wednesday, week 45): Deadline to submit your abstract
December 3 (Wednesday, week 49): Individual presentations (rehearsal)
December 10 (Wednesday, week 50): Deadline to submit your final report

Students wishing to be examined this semester must submit their abstract and report to Nick Volet by email before the above deadlines.

Exam format:
– Oral exam, total duration 20 min
– 10-min presentation followed by 10 min of questions

Further information is available via the study portal.


Storage

Slides and other files are available at this SharePoint site.

LaTeX files (for booklets and exercises) are available at this Overleaf project.