API Reference - Thin-Film Metrology

Overview

The thin-film metrology system provides a REST API for spectral reflectometry calculations and analysis. All endpoints accept JSON requests and return JSON responses. Base URL for local development: http://localhost:5000

Endpoints

POST /api/simulate_spectrum

Simulates reflectance spectrum for a thin-film stack using transfer matrix method.

Request Body

Parameter	Type	Required	Description
film_material	string	Yes	Film material code (sio2, si3n4, tio2, etc.)
thickness_nm	number	Yes	Film thickness in nanometers
substrate	string	Yes	Substrate material (silicon, glass, etc.)
wavelength_min	number	No	Minimum wavelength (nm), default: 400
wavelength_max	number	No	Maximum wavelength (nm), default: 800

Example Request

{
    "film_material": "sio2",
    "thickness_nm": 250,
    "substrate": "silicon",
    "wavelength_min": 400,
    "wavelength_max": 900
}
                

Response (200 OK)

{
    "wavelengths": [400, 405, 410, ...],
    "reflectances": [0.234, 0.241, 0.248, ...],
    "film_index": 1.46,
    "status": "success"
}
                    

POST /api/extract_thickness

Extracts film thickness from measured reflectance spectrum using optimization algorithms.

Request Body

Parameter	Type	Required	Description
wavelengths	array	Yes	Array of wavelength values (nm)
reflectances	array	Yes	Array of measured reflectance values
film_material	string	Yes	Film material code
algorithm	string	No	"lm" or "de", default: "lm"
initial_guess	number	No	Initial thickness guess (nm)
bounds	array	No	[min, max] thickness bounds

Response (200 OK)

{
    "thickness_nm": 251.3,
    "uncertainty_nm": 0.8,
    "chi_squared": 3.2e-5,
    "iterations": 12,
    "status": "converged"
}
                    

POST /api/fft_analysis

Performs FFT-based thickness estimation from spectral data.

Request Body

Parameter	Type	Required	Description
wavelengths	array	Yes	Array of wavelength values
reflectances	array	Yes	Array of reflectance values
film_material	string	Yes	Film material code
window	string	No	Window function: "hann", "hamming", "blackman"
detrend	boolean	No	Apply detrending, default: true

Response (200 OK)

{
    "thickness_nm": 248.5,
    "confidence": 8.3,
    "snr_db": 18.4,
    "peak_frequency": 497.0,
    "fft_power": [array of power values],
    "status": "success"
}
                    

POST /api/thickness_map

Generates 2D thickness map from spatial scan data.

Request Body

Parameter	Type	Required	Description
scan_pattern	string	Yes	"raster", "snake", "spiral", "random"
resolution_x	number	Yes	Number of points in X direction
resolution_y	number	Yes	Number of points in Y direction
film_material	string	Yes	Film material code
sample_size_mm	array	No	[width, height] in mm

Response (200 OK)

{
    "thickness_map": [[2D array of thickness values]],
    "x_positions": [array],
    "y_positions": [array],
    "statistics": {
        "mean_nm": 251.5,
        "std_nm": 3.2,
        "min_nm": 245.2,
        "max_nm": 258.7,
        "uniformity_percent": 2.7
    },
    "scan_time_seconds": 44.0,
    "status": "completed"
}
                    

GET /api/materials

Returns list of available materials and their optical properties.

Response (200 OK)

{
    "materials": {
        "sio2": {
            "name": "Silicon Dioxide",
            "formula": "SiO₂",
            "dispersion": {
                "type": "cauchy",
                "A": 1.4508,
                "B": 0.0036
            },
            "refractive_index_550nm": 1.46
        },
        "si3n4": {...},
        ...
    }
}
                    

POST /api/calculate_reflectance

Low-level reflectance calculation for single wavelength.

Request Body

Parameter	Type	Required	Description
wavelength_nm	number	Yes	Single wavelength value
thickness_nm	number	Yes	Film thickness
film_material	string	Yes	Film material code
substrate	string	Yes	Substrate material

Response (200 OK)

{
    "reflectance": 0.234,
    "film_index": 1.4596,
    "substrate_index": 3.48,
    "phase_shift": 6.283
}
                    

Error Responses

Status Code	Description	Example
400	Bad Request	{"error": "Missing required parameter: film_material"}
404	Not Found	{"error": "Material 'unknown' not found in database"}
500	Internal Server Error	{"error": "Fitting algorithm failed to converge"}

Rate Limiting

For production deployment, implement rate limiting:

100 requests per minute per IP address
1000 requests per hour per API key
Burst allowance: 20 requests