Ultrafast laser repair and diagnostics

The chain, and why it is the whole diagnosis

Ultrafast systems from different manufacturers share an architecture even when they share nothing else. Treating the system as a chain and finding the link where pulse energy stops being produced or stops being transmitted is the core of the diagnostic method. Everything else follows from it.

1. Pump source. A CW or pulsed pump, diode-pumped or lamp-pumped, with its own driver, thermal loop and protection. In many systems a separate boxed product with its own failure modes.
2. Oscillator. The mode-locked source that defines the pulse. Ti:Sapphire, fiber, or a seeded diode architecture, with a starting mechanism that can fail independently of the gain medium.
3. Stretcher. In chirped-pulse systems, the dispersive stage that makes amplification survivable.
4. Amplifier. Regenerative, multipass or fiber, with pump delivery, Pockels cell and driver timing, and cavity optics.
5. Compressor. Gratings, prisms or fiber, where alignment and grating condition determine whether you get pulses or a long chirped mess with the right average power.
6. Conversion stage. Where present, an SHG, THG, OPO or OPA stage that cannot exceed what the fundamental delivers to it.
7. Feedback and control. Monitor photodiodes, converter stages, interlocks, trigger and synchronization, and the software path.

A system delivering correct average power with a wrong pulse duration is a compressor or stretcher problem. A system delivering correct timing with no energy is an oscillator, pump or amplifier problem. A system with healthy fundamental and weak converted output is a conversion problem. These are different jobs, and telling them apart before opening anything is what a competent evaluation buys you.

Failure symptoms we are asked to evaluate

Four diagnostic traps

These four are worth eliminating before anything invasive happens, because each one can produce a symptom that looks like a different fault.

1. The displayed value is not a measurement

Many systems display the commanded setpoint rather than a sensed value. If the command reaches the display layer but not the current driver, the panel reads perfectly while nothing changes physically. Measure the drive current at the hardware and establish whether the readback path is a measurement or an echo.

2. Timing is not lasing

Trigger and synchronization electronics run independently of the optical chain. A clean repetition-rate reading and a healthy sync output confirm the timing board. Whether optical pulses exist is a separate measurement made with fast photodetection on the real beam.

3. Average power is not pulse energy, and pulse energy is not pulse duration

A thermal power meter integrates. It will happily report the correct number for a system whose compressor has drifted and whose pulses are ten times longer than they should be. If the experiment depends on peak intensity, average power tells you almost nothing on its own.

4. The last stage is blamed for the first stage

When a system with a conversion stage produces low visible output, the crystal is the intuitive suspect and usually the wrong one. Second-harmonic generation cannot produce more than the fundamental delivered into it. This is set out in full on the SHG and harmonic generation page.

How an evaluation runs

1. As-received condition report. Configuration, labels, connections and shipping condition recorded and photographed before anything is changed.
2. Configuration verification. Every module label read separately. What the system is takes precedence over what the record says it is.
3. Bring-up and infrastructure. Supplies, cooling, interlocks, protection states and control communication established, and readback values checked against physical measurement.
4. Measurement and fault localization. Output characterized by wavelength on a defined path, the optical pulse train verified, and the chain divided until the fault sits in one subsystem.
5. Written findings and your approval. What was measured, what was found, what remains unknown, and the repair options with their cost and risks. Nothing is repaired, substituted or modified until you approve the scope in writing.
6. Repair, validation and return. Work inside the approved scope, then electrical, optical, timing and functional validation, a written service report and documented packing.

Measurements defined per project

Every engagement names its measurements before it starts. PhaseX defines and provides the measurement capability the project requires. Depending on the system and the question being answered, that is owned, rented or qualified third-party measurement resources arranged as required. The evaluation proposal states which measurements will be made, by what method, and where each one comes from, together with the acceptance criteria the work is judged against.

In-house instrumentation currently includes a RIGOL MHO984 oscilloscope and a Joulescope JS320 for electrical, current, timing and pulse-train work. Optical metrology is specified per project and provided through owned, rented or qualified third-party measurement resources arranged as required and named in the proposal. We do not publish an equipment inventory in place of a measurement plan, and we do not offer manufacturer-equivalent calibration or certification to original published specifications where the original acceptance data and the corresponding standards are unavailable.

Platforms and manufacturers

We provide independent service and repair support across the platforms below. Configuration, parts access and required metrology decide the scope of a given job, and we confirm both with you before anything ships.

Manufacturer pages

Additional platforms supported

Required shipment components

A system that cannot be brought to its normal operating state on the bench cannot be diagnosed. For bench evaluation we normally need:

• Laser head
• Controller
• Power supply
• All interconnecting cables, including any with a non-standard pinout
• Any dedicated module required for normal operation, including conversion, trigger, pump or paired units
• Control software, license files and interface documentation, including a MATLAB or LabVIEW control path where that is how the system is driven
• Manuals, configuration sheets, acceptance data and prior service reports, however incomplete

On discontinued platforms the customer's own paperwork is frequently the only surviving record of the configuration. Send it even when it looks irrelevant.

International shipments

We receive systems from outside the United States, including from Canadian universities and research institutes. We provide the commercial documentation a repair shipment normally requires and coordinate with your shipping office. Customs classification, duties, temporary import treatment and clearance timing remain the sender's responsibility, and we do not give customs guarantees. Insurance is the sender's decision and should reflect replacement value. We document the as-received condition on arrival, which is the evidence you would need if transit damage has occurred.

Scope and safety

Two limits

We are direct about the work we take on, so we are equally direct about the two boundaries.

• We do not promise a specific repair before diagnosis. The diagnostic evaluation comes first and the repair scope follows from it. A finding that a system is not economically repairable is a legitimate result, and it is delivered in writing.
• We do not certify a system to original published specifications where the original acceptance data and the corresponding standards are unavailable. We document the measured condition on arrival, the fault found, the work performed, and the measured condition on completion.

Warranty

If your system is still inside its manufacturer warranty, use the manufacturer, or get written authorization from the seller first. Our work is out-of-warranty and legacy equipment, which is where the support gap sits in any case.

Laser safety

Class 4 work is planned and executed under a project-specific laser safety plan. The required engineering controls, personal protective equipment, beam management and facility conditions are defined in writing before any energized optical work begins, and the infrastructure that plan calls for is provided within the project scope. Where a laboratory's own controls are involved, final hazard analysis and approval stay with the institution's LSO or EHS function.

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