Hi
As per my understanding you want to display legend in your plot, but you are unable to see it as it is behind the axes ax2.It is because of the differences in dimensions of ax1 and ax2 .
You can simply do the following change in the code
ax2.Position=ax1.Position;
I can demonstrate the same with some changes in your code.
%% Plot Raw data with two x-axis
load("matlab.mat")
lim_1 = 600; % Enter the limits here for the plot
lim_2 = 900; % Enter the limits here for the plot
wv_tik = lim_1:50:lim_2; % Modify this if needed
E_tik = round(1240./wv_tik,2);
figure;
for i = 1:length(Data)
plot(Data(i).data(:,1), Data(i).data(:,2), LineWidth=1.5);
end
ax1 = gca; % get current axis
ax1.XColor = 'k'; % set bottom x-axis color to black
ax1.YColor = 'k'; % set left y-axis color to blue
ax1.XLim = [lim_1 lim_2];
ax1.XMinorTick = 'on';
hold on
% Add a second x-axis on top
ax2 = copyobj(ax1,gcf);
ax2.XColor = 'k'; % set top x-axis color to red
ax2.XTick = wv_tik;
ax2.XLim = [lim_1 lim_2];
ax2.XTickLabel = E_tik; % remove tick labels for top x-axis
ax2.XAxisLocation = 'top'; % set location of top x-axis
ax2.YTick = []; % remove tick marks for top x-axis
ax2.XMinorTick = 'on';
xlabel('Wavelength ($\mu$m)', 'Interpreter', 'latex', 'FontSize', 14);
ylabel('PL ', 'Interpreter', 'latex', 'FontSize', 14);
set(gca,'FontSize',14); % set font size for the axis labels and tick marks
legend('Juni','Interpreter', 'latex', 'FontSize', 14, 'Location', 'eastoutside');
ax2.Position=ax1.Position;
Now you can see your expected result. I hope this resolves the issue.
