QBerr wiki

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====== History and versions of QBerr ======

Initial steps of ellipsometry application development took place in the Department of Condensed Matter Physics, at the Faculty of Science, Masaryk University, Brno, Czechia. The department has a long history of ellipsometric research led by Josef Humlicek. The author of QBerr, Premysl Marsik, started his PhD studies at 2004 under the supervision of J. Humlicek and started building his first ellipsometer, including a data acquisition software.

At the time, the lab used a data processing program written by J. Humlicek called **AB2PD**, which stands for Alpha Beta to Psi Delta. This program takes raw rotating-analyzer ellipsometry data in .sig or .big format, extracts modulation parameters alpha beta, and calculates the ellipsometric Psi and Delta spectrum. It includes a calibration algorithm for corrections of offsets between nominal and actual azimuths of polarizer and analyzer. Data are saved in a file format **.EPD** (Ellipsometry Psi Delta).

Another program by J. Humlicek, called **LOOKDATA**, served as a viewer for the raw .sig and .big files. Both of these legacy programs were working on command line without graphical interface.

In 2005, P. Marsik wrote programs **LookData2** and **mab2pd**. The LookData2 provided a GUI, and enriched the functionality of the LOOKDATA. The multi-ab2pd was a GUI based RAE calibration software, which added support for multiple RAE files taken at various polarizer azimuths. In 2006, P. Marsik built a rotating compensator ellipsometer together with a data processing and calibration software **CalibRCE**, and later in 2007 software for analysis of optical properties of thin films, called **MFF** - multi film fit.

Somewhat retroactively, we loosely attribute these programs to the first generation of QBerr.

===== QBerr 1 =====

The source code for programs in this generation is written in Pascal with GUI developed in Delphi framework.

In 2009, P. Marsik moved to the Deparment of Physics, University of Fribourg, and started building a Time-domain THz ellipsometer, while also working with FTIR based infrared ellipsometers. The TD-THz ellipsometer was controlled with software called **THzElli**, which also had to produce compatible data files. This led to further software development and modifications of the libraries for the needs of the ellipsometry lab in Fribourg, together with data format standardization.

Many versions of **mab2pd** and **LookData2** were deployed in the lab between 2010 and 2019, and some versions were also used on synchrotron-based IR ellipsometers at ANKA, Karlsruhe in Germany, and at NSLS, Brookhaven National Lab in the United States. LookData2 is still in use in 2026, with most recent update is version 2.1.4.0 from 2024 modified for data format produced by new ellipsometer at NSLS-2 in Brookhaven.

About 2012, a new file format was introduced, **.epdx**, which is a XML wrapper for metadata and CSV data conforming with the original .epd format.

Between 2010 and 2015, new program for analyzing and modeling ellipsometry data was developed, called **Berreman**, in honour of Dwight W. Berreman. It implemented his 4x4 matrix method for calculation of wave propagation in generally anisotropic and optically active media. Curiously, the solution to the 4x4 problem was done analytically using the Cardano and Ferrari formulas. The Berreman software included new DataMan operating with the metadata-rich .epdx format, and introduced the possibility to open any number of graph windows, alowing views on multiple datasets and the dielectric function model side by side.

The lastest version of Berreman is 1.2.10.7 from november 2016, after that date, new software in the 2nd generation started to be useful.

===== QBerr 2 =====

Year 2015 marks the start of large rewrite of the codebase from Pascal to Qt/C++. Qt framework and development environment was chosen for its cross platform support, good GUI design tools, but also due to the existence of excellent open-source graph-plotting component [[https://www.qcustomplot.com/|QCustomPlot]]. The name //QBerr// was coined to denote the Qt-written collection of libraries.

As a first step, the libraries supporting .epdx data standard were ported to C++ and generalized for storage of time-domain spectroscopy data in the .meax format.

Next step was completely new implementation of CalibRCE 2.0 - software for processing and calibration of rotating compensator data in the context of mid-infrared ellipsometry.

FIXME

CalibRCE, thz meax processing (meas2meax) QBerr 2 SampleBuilder

2019 mab2pd2

LabApps and LabLisp starts

CalibRCE 2.5 eventually abandoned, code reused for mab2mm

===== QBerr 3 =====

2023 THzElli 2, lot of coding in 2024 (THZElli_LOG)

2025 LookData3, mab2mm

tighter integration with LabApps and LabLisp, support for parallelization and LabLisp scripting

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